City of Heroes

This game can be summed up in one statement: it's all downhill after character creation.

First of all, it should be noted that CoH suffered along with its competitors from the death of the 'MMO' concept. It was originally planned as a series of large mostly outdoor areas in which dozens of players would spontaneously compete or team up to chase down mobs, with only a few missions being instanced. Though this invariably took the form of 'kill ten rats', there were at least some attempts to make it interesting. For instance, the original form of a low-level mission targeted mobs which only spawned at night at the top of apartment buildings, requiring players to scramble up fire escapes and hop from rooftop to rooftop.
Gradually, the game slipped into the usual instancing. It never got the chance to be an MMO and became just another small-team PvE game. This at least, can be blamed on the stupidity of the industry as a whole.

More surprising is the extent of the developers' uncertainty as to what the game should be. It is one of the best examples of the potential damage done by the "customer's always right" mentality. Anything that seemed popular was thrown in there, with no thought to whether it fit into the larger concept, or any attempt to make it fit. There's no point to going into much detail, so i'm only giving the most glaring examples.
PvP is laughable, since the game was never created with it in mind and cannot be balanced for it.
Gigantic stretches of the game world were created based on the vague notion that players like farming endless numbers of mobs and are simply taking up space because players have absolutely no use for them, nothing new to do or see there. 
Even something so potentially useful as letting customers create their own content ended up a complete debacle because they were given rewards for it, which meant everyone started leveling their characters to maximum while never even playing the game, just running the same player-created missions for the quickest, safest exp grinding possible.

Slowly, the game has even lost its comic-book feel. Its selling point was the superhero precept, defending the innocent, foiling nefarious plots by cackling mad scientists, running around in ridiculous tights and capes. There should never have been any question of moral depth. CoH was cheesy, it was shallow and predictable; it was, simply put, superheroic. It was greatly damaged by later attempts at moral ambiguity, mystery or real drama. There's simply not enough wiggle-room in the very concept of co-op PvE games to allow for that. You team up and beat on some bad guys. Good, clean fun. Morally simplistic as it is, that's golden-age superheroism, and CoH did it well enough at its start.

As content piled up though, there were more and more 'story' missions obviously intended to be soloed, with endless cutscenes trying (and failing) to create tension and drama. Even the original driving, bombastic theme music has been abandoned.

One decent feature is the game's class system. The original archetypes were based on the standard nuker/tank/healer triad of co-op PvE, with crowd-control and a soloing class thrown in, and in a remarkable display of honesty they were even named tankers, defenders, blasters, and controllers. Within those archetypes, the developers gave a remarkable variety of combinations with skillsets of different classes complementing each other. There were 'defenders' that didn't heal, relying on force fields, tanks with low resistances but which could self-heal, controllers that did almost no damage and others that were almost blasters. That only some of these were ever used was the fault of the players, not the game itself. It was hard to find any non-viable option, given the right teammates. Even later class additions from the expansions, while not as inspired, were mostly valid twists on the original archetypes.

Well, there is only one truly good aspect i can mention about the game, and that's its aforementioned character creator. Along with Spore's creature creator, it has managed to let me visualize some of my ideas and even supplied me with some others. Whether it's a cyborg werewolf, a teleporting robot looking for its master, a gravity-manipulating outer-space automaton, a winged, storm-summoning supersoldier or a mad scientist who replaced his skin with an exoskeleton, i've gotten quite a few good laughs out of mix-and-matching parts in the costume design screen.

I still like the characters CoH helped me create. If only there were some incentive to actually play them.