I am going to concern myself with these two examples since this is where the crux of your more options for melee monsters/NPC's lie... and actually I will have to comment on the Bulette later, but I will quickly comment on the Bugbear...
Our 4e Bugbear is a level 5 monster (I'm not certain how it compares to the CR 2 3.x Bugbear), who has a simple melee attk w/ a morningstar (easily covered by the 3.x Bugbear), it has Skullthumper... which is an attk that requires combat advantage and a morningstar... it does the regular damage for a morningstar but allows the bugbear to knock an opponent prone and daze him. Finally Predatory Strike allows the Bugbear to deal extra damage 1x per encounter. He can also, per 4e rules,... charge, bull rush and grab.
Our 3.x Bugbear already has a morningstar basic attack... now for one of his racial feats lets give him power attk... he can now deal extra damage anytime he wants by taking a reduced chance to hit. He also has a ranged attack with the javelins... so we're already at three different options by just switching a feat out... a regular attk, power attk and ranged attk. On top of this he can implicitly grapple, trip, feint, sunder, bull rush, charge, disarm, overrun etc. I'm not understanding how your 4e Bugbear has more options in combat by the rules?
Well, I think others may have had a different experience than you did with the extra combat options. At least in my experiences, most DMs avoided having monsters grapple, trip, sunder, disarm, overrun, etc - unless the monster was designed for it. Because typically it was a weak option, and for most DMs, required picking up the PHB and looking through those rules every time it actually came up.
Similarly, when a DM grabbed the Monster Manual to run a group of bugbears, most aren't going to start swapping their feats on the fly to expand what they can do. Instead, they will end up with a group of identical monsters that do pretty much one thing - hit people with morningstars. And occasionally throw javelins if they need to.
When I grab some in 4E, they will hit people with morningstars - and smash some enemies to the ground, while their buddies pop up and strangle them from behind. Even if they don't have a huge host of options within that, each round feels a bit more fluid, a bit more dynamic.
And even more important - a bit more distinct to the monster itself. The complaint against melee attacks in 3.5 was that everything pretty much came down to rolling to hit and dealing damage. A group of bugbears and a band of earth elementals and a handful of hill giants all swing their weapons/fists/etc at the PCs, and do some damage. Note that even adding class levels and feats doesn't change things too much - rage might alter a monster, but it is still just rolling attacks and dealing damage. A ranger might get more attacks from two weapons, and deal more damage to certain enemies. A fighter might be more accurate, a rogue might deal lots of damage with sneak attack, and people with power attack can trade accuracy for damage. But again - melee guy rolls to hit, and deals damage. In 4E, each enemy tends to have some unique flavor that plays out differently.
Now, I'm not by any means saying all melee monsters in 3.5 were identical. There were certainly special abilities that keep things distinct, whether it is poison or regeneration or actually investing in the feats to trip/disarm/grapple.
But the default options for melee attackers tended to be much more limited, in my experience, than the default abilities for most enemies in 4E.