I seriously dislike fighting games that are complicated. And by complicated, I don't mean ones that call for strategy. Those are great. I mean the ones where any move worth anything calls for an intricate, precisely timed 20-button combination, and you need to memorize a couple dozen of those, plus when to use each one before you can get anywhere. You know the ones, Soul Calibur, Tekken and so forth.
What I like? Balance is nice. Fancy moves, interesting and quirky characters, lots of characters, customization is sometimes nice, and the sort of fights that will make you think "wow, that was awesome" every few matches are always good when playing against a friend.
So, on that basis. SSB Brawl gets second place (still bitter that they replaced Mewtwo, but this has nothing to do with its ranking), Powerstone gets third, tied with a few Gundam games. Some of them are surprisingly good.
First place goes to an indie game you may well have never heard of. I'll likely get lynched for this, but Touhou Hisoutensoku (UNL to some). Excellent game, if you can stomach Touhou, plus it somehow fuses fighting/bullet hell/card games and gets away with it. Incredibly fun game, anyway, which I was introduced to by my younger sister a couple months back.
Anyway, I heartily recommend all of the above to anyone who enjoys fighting games, unless you like your complicated moves (I know some do). If anyone's interested in playing Hisoutensoku, getting it to function with all characters and so on (since it's technically an expansion pack, sorta) is a bit tricky, so please PM me and I'll walk you through it. You're missing out on an excellent game otherwise.
...Wow, large post. Sorry about that, I ramble far too much.