Way back in the day I would've said Sierra or LucasArts, these days I gotta go with Blizzard. They may take a while between releases, but the amount of work they put into 'em are reflected the ravenous reactions they get from their fans. Having played Starcraft II already, I think their best games may still be ahead of them.
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Talent, vigor, drive...
You'll eat peanut butter the rest of your life.