Co-op RPG's. More should be made! How many RPGs are co-op, online or otherwise?
In the case of games like Tales of symphonia/vesperia and Eternal Sonata. Having someone to fight things with, or be your chauffeur when you don't want to walk across the world map, get fetch quest number infinity, (My friend won't stop making fun of my 30 minute usage of stores in vesperia) is great. If we can enjoy either the combat or the story, (God Forbid Both) then it's perfect.
Isn't it easier to do then say, Split screen? Is the balancing for a human controlled player more of a challenge then balancing for 3 extra AI party members? Even if it's like deathspank, where the 2nd player can't level or anything, that's better then nothing at all. I mean if you already have a game with more then one party member, or multiple interchangeable party members, that does not shoot bullets which necessitates split-screen, why not let controller two have drop in drop out functionality.
What's wrong with couch co-op Dragon Age? Co-op Final Fantasy? Co-op makes everything better right? Work on this Japan! If you create another Star Ocean, give me some Co-Op.
For the record, I've only played Torchlight, So while I would Imagine Diablo falls into this category somewhere, I don't know where. Huzzah!