Rogue Agent
First Post
3e was closer to 2e and probably closer to 4e then 4e is to 1e
It depends heavily on how you look at it.
OD&D to 1E: The big shift here was in the number of rules. The AD&D core rulebooks were very explicitly attempting to create an "official" ruleset; whereas OD&D was basically written to be unplayable unless DMs customized the rules.
1E to 2E: 2E brought back in the attitude of DMs customizing the rules, but very little actually shifted mechanically between these editions. But some people saw a big shift from OD&D/1E to 2E in terms of attitude; fantastical content; and the resources provided to DMs.
2E to 3E: In this shift, 3E mucked around with the core of the system (unifying resolution mechanics, getting all the math pointing in the same direction, etc.) but left everything else practically untouched (resulting in virtually identical gameplay).
3E to 4E: In this shift, 4E did the exact opposite. It mostly uses the same core resolution mechanics as 3E, but changes everything else (classes, spells, etc.), resulting in completely different gameplay.
So what metric are using to make your comparison?
Attitude? Then 2E is a lot like OD&D in its inclusion of optional rules; very different from AD&D in that respect. AD&D is very similar to 3E in terms of its support for dungeoncrawling. 4E is very similar to 2E in practically abandoning dungeoncrawling and focusing on railroaded stories.
Core mechanic? Then OD&D w/Chainmail is distinctly different from everything that followed. But OD&D w/o Chainmail, 1E, and 2E are all very similar. 3E is different than what came before, but very similar to 4E.
Functional gameplay? Everything pre-2008 is pretty similar; 4E is very different.
And, of course, the game has reliably added more options for customization with every new iteration. For some people, the game is suddenly considered "very different" as soon as the customization options for PCs exceeds whatever their personal level interest is. More than three classes and four races? Total munchkin-ville! Non-weapon proficiencies? Crutches for the imagination! Feats and skills? The min-maxer's wet dream! Powers allowing for selection of class features? Unnecessary meta-gamey nonsense!