I personally always went X > Classic > Legends > whatever, when we're talking Mega (if we're talking looks for the blue bomber, of course. For games in the franchise, I still say the MMZ saga was better than most of the X saga, at least to me). I dunno why, because I usually tend to go for the stylized, childish versions of most characters, which would mean Classic, but something in the X series clicked with me, I guess. So for me, it's X for Brawl, if possible.
Oh, and whoever said Bass.EXE looks bad, you need new eyes, man. He was pretty much the only reason I gave that game a chance - because Bass being back, looking more awesome than ever, is more than enough of a reason for me to check it out