I don't really like classes, but that's because I prefer to play characters who can do everything and this is often hard to do when you have to battle the preassigned "role" of a class system. Once I've played through a game as the Jack of All Trades I don't mind trying out the Glass Cannon types, though, so I enjoy games where you can make heavy tradeoffs *similar* to the ones in class systems.
But a class system with VERY FEW flexible classes (a la Mass Effect or Jade Empire) just bores me to death. There just aren't any REALLY COOL options to try out once you've figured out how to play the game, so I can't go back and try being that complicated Glass Cannon and unleash the thunder.
The way I see it, if you're going to do classes have a couple easy or medium-easy classes that can do pretty much everything in an okay way, then several very difficult-to-play classes that can just be DISGUSTING if you play them correctly. Or, have unlockable classes that are more powerful than the standard ones. Something so that the game will continue to be interesting.
And [rant] FOR GOD'S SAKE IF THERE ARE TWO CLASSES THAT BOTH CAN HAVE ANIMAL COMPANIONS--NOT FAMILIARS, ANIMAL COMPANIONS--THEN EITHER MAKE THEM STACK OR MAKE IT SO YOU HAVE TWO ANIMAL COMPANIONS, DON'T MAKE THEM REPLACE EACH OTHER BUT BE STUCK AT A CRAPPY LOW LEVEL BECAUSE IT BY GOD NEVER OCCURRED TO YOU THAT SOMEONE MIGHT ACTUALLY WANT TO TRY RANGER/DRUID. FUCKERS.[/rant]
Ahem. Sorry, I'm done now.