Favorites
Delfino Plaza - Like TheTuninator said, it's great at keeping things fresh and changing things up while retaining a competitive atmosphere the entire time. There's tons of map variety, which keeps the battle exciting throughout. It's also visually appealing, has great music, and comes from a fantastic game. I was seriously boggled at how accurate it was to the original location from Mario Sunshine. Definitely a top tier stage.
Fountain of Dreams - I'd say this is probably my favorite stage ever. The visuals are fantastic, the music is booming and outstanding, and the size is just perfect. I understand why some Melee players dislike this stage, but I actually like the moving platforms. They create some interesting positioning scenarios. On top of all of that, it does well to represent an iconic location from the Kirby series. I really want to see this stage return.
Mushroom Kingdom (64) - I love this stage. Very fun for FFAs and teams. The warp pipes are cool, and I like how KOs off the bottom, top, and sides are all viable kill methods.
Peach's Castle (64) - There's something about those 64 Mario stages. I don't really know why I like this one. Maybe it's the large screen size but small stage size. It feels compact enough so that the fighting is centralized and doesn't get broken up, but open enough for there to be breathing room. The sliding platform at the bottom provides for some hilarious shenanigans.
Smashville - It's basically Final Destination with a more appealing aesthetic and a platform. What's not to love? Plus, it's Animal Crossing. I love Animal Crossing.
Least Favorites
75m - I thought this was a great idea for a stage even before it was revealed, but its execution was absolutely terrible. They should've just created an original layout based on Donkey Kong's construction site. What we got instead was a lazy recreation of a map that is counter-intuitive to Smash's gameplay. I'd like to see the Smash team retry this one, but design their own layout instead. It could become something great.
Mario Bros. - Another great idea, but in this case I don't think it could have been saved. Its layout just lends itself too much to an enclosed environment with no way to kill off the top. Altering the inordinate strength of the enemies or removing them entirely could have alleviated the frustration somewhat, but it still wouldn't be a very fun stage to play on.
New Pork City - No, just no. A great idea for a location to base a stage off of, but a terrible stage to fight on in execution. Nobody ever dies here. With how defensive Brawl is, stocks go on forever on this stage. Even hits that would guarantee kills on other stages can fail to KO here. The stage is just too dang big. Even with four players, it feels empty.
Temple - See NPC. To be fair, I don't think its design or even size is nearly as awful, but it's much less fun in Brawl (again, it takes too long to kill), and I think I'm just sick of it after all these years.
Sky World - Don't like the under-stage play, don't like the breakable flooring, don't like the game it comes from.
Spear Pillar (with Palkia or Cresselia) - Palkia's camera flips ruin the pace of the match, and Cresselia never shuts up or stops attacking. I don't like the layout much either, even though I like the idea of the stage. For that reason, I'm not too fond of the Dialga version either, but it's not bad or anything. I just don't care for it one way or the other.