I think that many people had a very different experience than I did with earlier editions of the game.
I started playing D&D in 1986 at the age of 12, with the "Red Box" D&D Basic Set (1983 Mentzer edition). The one with the Elmore painting of a red dragon on the cover, with all the interior art done by Elmore and Easley. We moved on quickly through the Expert, Companion, and Master sets -- nobody seemed to care for that silly rule about never being able to gain more than one level in a game session.
I started borrowing bits from AD&D in my games and after a year or two had pretty much switched over to the AD&D rules completely. I bought the 2nd Edition rules as soon as they came out (and had already been using some of the changes previewed in the Dragonlance Adventures and Greyhawk Adventures hardcovers), as well as all of the "Complete" PHBR series of books and Player's Option books (although by the mid-nineties I was losing interest).
Sense of entitlement certainly varies from one player to another, but I honestly haven't seen a difference between players in 3.x edition and players in any earlier edition that I have played. It's a personality trait, not an edition trait. I've had players in AD&D 1e complain after the first adventure in a new campaign, "gee, it at least would have been nice if you'd given us enough XP to get to 2nd level." Or complaining about still finding +1 magic weapons when their characters with 6th or 7th level, because "we should be getting +2 weapons by now."
I'm not sure that I agree that 1st Edition was more of a "DM's game" and 3rd more of a "Players' game" -- but I think there was a more adversarial us vs. them mentality in a lot of the earlier gaming literature. Articles and advice on how the DM can relieve the PCs -- once again -- of their hard-earned treasures in order to keep "game balance" in check always rubbed me the wrong way.
The oft-praised 1e insistence on having pretty much anything of value extremely well-hidden and/or guarded by deadly traps, making the PCs bleed for everything they get simply leads to precious game time being wasted on tedious and pedantic searching procedures. I've played in groups of (and run games for) players who insisted on searching every square inch of every room and hallway "because that's where the DM probably hid the treasure." And when they find it, it reinforces this behaviour. These same groups of players won't walk anywhere without probing the floor in front of them with a 10' pole, and won't enter a room without throwing various items in ahead of them. It just makes me want to scream, especially when I'm DMing the game and I just want to get on with it already. At least Take 10 and Take 20 helps me keep my sanity in these type of situations. It's never the newer players who do this in games I've played in, just the ones weaned on late 70s and early 80s AD&D and D&D games.
To my way of thinking, powerful and/or useful treasures are almost never going to be found hidden somewhere inconvenient or locked up in a room. They are going to be actively used by the PC's foes, and are part of the reward for overcoming that challenge. Nobody is going to set deadly traps in areas where they or their minions are likely to set them off by accident. Random drawers, chests, and doors are not worth anyone's effort to set a trap on unless there is something awfully valuable in there -- or unless they want to keep nosy adventurers out. But early AD&D and D&D adventures were full of arbitrarily or randomly trapped doors, chests, drawers, etc that didn't seem to serve a purpose other than to keep PCs on their toes. I think there are better ways to do that which don't result in players being ridiculously cautious about everything.
I agree that there was an "expected wealth by level" that was implicitly assumed by the game as far back as I've every played it. A number of adventure modules even stated up front that characters will have a very difficult time if they don't have particular items or spells. Pre-generated characters in modules had treasure "appropriate" for their levels, and the DMG and MM had "Monster Levels" as a way of assessing the general toughness and appropriateness of monsters versus PCs of a particular level. A 12HD monster that can only be harmed by +4 or greater magic weapons certainly assumes a certain level of wealth and range of character levels. 3e simply gives actual guidelines on this so that DMs don't have to resort to having PCs items "stolen" if they were over-powered. The DMG clearly says that they are guidelines but warns DMs to consider all of the far-reaching implications of deviating too far from the base assumptions. And it warns DMs that if they give out less treasure, then the PCs will be weaker for their level than "average" and opponents of a normally appropriate CR may walk all over the PCs as a result.
The PHB 3.5 still clearly states "CHECK WITH YOUR DUNGEON MASTER" as the first step of character creation on page 4, and explains that he or she may have house rules which differ from the published rules. In the DMG 3.5, under the sections regarding the "role of the DM," it clearly states that the DM is in charge of the game and is the final authority on the game rules, even overriding rules that have been published. \
In that same section of the DMG, it does say that DMs shouldn't change the rules without giving the players a good, logical explanation for the change, and I have to say I agree wholeheartedly with that. I've played in a lot of games in earlier editions with DMs who instituted what I can only call not very well-thought-out changes to the rules that were often either unfair or unnecessary and often didn't improve the game -- but they satisfied that particular DM's view on how the game should be played (almost always to make it more "gritty" and "realistic"). I remember one game in which the DM required Wizards to hold their spell books open to the spell they were casting in order to cast a spell. He loved the images in the Gargoyles cartoon of wizards casting spells like that, and wanted that image in the D&D game as well. After discussing it with him, it was obvious that he hadn't really thought through the implications it would have on that game, and he dropped it.
The DM is running the game, but I object to the attitude that it is the DM's game, and if a player doesn't like it, he can go play somewhere else. It's the group's game, and the DM's ultimate "job" is to make sure that everyone has fun. That doesn't mean making things easy, fudging rolls to not kill characters, catering to one whiny player's desires, or any of that nonsense. The DM ultimately controls the pacing and events of the game, and it's a very self-absorbed DM who runs a game solely to satisfy his own idea of what a game should be. And I've seen DMs trying to push their "superior blend" of gritty, "low magic," "low treasure" style of D&D on players who didn't really want it for 20 years, regardless of edition.
I've played enough D&D with half-baked, unfair, or just plan stupid house rules that I completely agree that DMs should be held accountable for the deviations they make from the rules. If the DM is going to change something, there should be a good reason for it, and the changes should be well thought-out. If one of the DM's roles in the game is to be a referee and arbiter of the rules, then those rules need to be fair to everyone involved. And players shouldn't be asked to just blindly accept rules that don't make sense simply because the DM decided the world should work that way. That doesn't mean that players should be able to veto house rules just because they don't like them -- but I have trouble accepting a house rule unless it makes sense (even if I don't like it).
PCs haven't been leveling up significantly faster in 3e games in which I have played. But I haven't really played games in any edition where the players legitimately advanced from 1st level through any higher than about 8th level. It usually took 2-3 sessions of play to gain a level through the early levels back when I played 1e or 2e, and it hasn't really changed in 3e, from what I can see. And there is the oft-noted difference that 3e has been re-designed and re-balanced so that players will advance through to 20th level if they play long enough. A 12-level 1e character and a 12-level 3e character are not directly comparable, even though at first glance they may have similar hit point totals, base "to hit," access to spells and so on. Monsters are generally a lot tougher, and can do a lot more damage to PCs than in previous editions.
3e was designed to actually use all of this high-level stuff that most people never actually got to in previous editions. So that is one fundamental difference in editions -- 3e is actually designed to be played at those higher levels. Sure, you could play 20th level characters in 1e, but it was pretty clear from most of the published material that the game was pretty much designed around the 1st to 10th level game. The D&D Companion and Master (and Immortal) rules sets were about the only other real effort to make ultra-high levels really playable.