The force multiplier effect was one of the stellar attributes of CoH's system. You could throw together a motley collection of relatively poorly built characters and then do amazing things.
In the incarnate trials, with players who had extra incarnate abilities and who built well, and the group would be greatly more than the sum of the individuals. Then, add effective leadership and people who tried to be good followers, and then it just flowed beautifully.
None of the MMO's I've played since have had that kind of synergy. For those, it's always seemed to be either weak synergy, or just check-the-box role filling with gear checks.
I noticed that with DCUO, that in many ways its all just whatever roles you have and the gear those roles have, alot of the time. While role confinement in DCUO so far hasn't been outright extreme, it's still annoying enough to me when some jerk asks for the controllers CR(and ONLY the controllers, they act extremely rude to anyone who plays the controller class). But the game still suffers overall from trinity grindfest, and I don't really feel like a super hero in the game, just another grunt at times. Others try to convince me I'm good for nothing but a battery for their power meters as they power dump all the time, and perform badly, which only serves to annoy me and remind me how much funner city of heroes was overall.
I played a time manipulator, I blasted alot with fire or energy blast. If not those, then gravity control was my offense. I debuffed enemies, buffed allies and even healed behind the sheer amount of control or damage output I did, I felt super because of that. And I also felt super because I could defend myself, without relying on someone to be the only reason I live in some situations. In many ways, mmorpgs suck as games, cause the player doesn't get to really be an individual in them know?
City of heroes encouraged teamplay and encouraged you to be your own individual at the same time, it was just brilliant, and it was it's depth that let people do that.