Hey, I was thinking of doing a poll but there are a lot of new stages and frankly it is tough to just pick one that is the "best", especially if you are like me and just started playing the game a few days ago. Wondering what everyone's favorites are so far though.
Personally I haven't really unlocked too many so I can't comment on much beyond the default ones.
PS. Feel free to spoil away and post all kinds of unlockable stages. Those who do not want to see spoilers should not have come in here. I totally spoiler tagged this thing!
At the moment though I'd say:
Spirit Train - I've made it clear before that I love trains, but this stage is pretty sweet either way. It's pretty dynamic without being too dynamic. I feel like it is a stage where positioning constantly matters... I'm always fighting to get the best spot. And how it quickly shifts the camera and you have to scramble to stay on screen is pretty neat too.
3D Land - Although I love Rainbow Ride, I'm really not super fond of the sidescrolling stages in Smash in general. This one seems to really nail it though. Lots of fun platforming bits without being too crazy.
Tomodachi Life - Not sure why this one appeals to me so much. It's a pretty simple stage, but I like the simplicity here. Kind of neat that it is more vertical than horizontal, that seems kind of rare in Smash Bros. stages.
PAC-MAZE - Recently unlocked this one and I really like the "gimmick". Actually, I feel like they pretty much nailed every Pac-Man element in this game, period. Great use of the license.
Gaur Plain - Actually, I'm not really sure if I like this stage or not. I might end up getting very annoyed by it. But for now, it seems cool. I like how "dangerous" it is. Yeah you can hang out on the top, but that's lame. Gotta go down on the tiny platforms below and battle it out. Also it is Xenoblade, and Xenoblade is awesome.
I could probably list more because I really like a lot of the stages so far, but it would sort of defeat the purpose to list most of the stages or whatever.
On the other hand, not entirely enthusiastic about the stages they decided to bring back. WarioWare is amazing and Corneria is a classic, but the others? Kind of meh on them. My vote for worst stage in the game so far is... Mushroomy Kingdom. Nintendo should have known better than to bring this sucky stage back.
Magicant, Tortimer Island, and Gaur Plains are my top favorites so far. Granted, I wish the Flying Man gimmick wasn't part of Magicant, but I adore everything else about the stage. I also really like Dream Land, even though it's kind of bland (just recently found out that the color can be swapped to B/W by holding L). I don't usually like moving stages AT ALL, but this one kind of works for me. Lesser favorites, but still favorites are, Arena Ferox, Spirit Train, and Gerudo Valley.
I'm cool with a lot of them. Granted, there are a bunch I haven't spent a lot of time with (apparently there's a top to Unova Pokemon League?) but there aren't any real stinkers from what I can tell so far.
Top 10 new stages 10. Tomodachi Life 9. Gerudo Valley 8. Unova Pokemon League 7. Find Mii 6. Spirit Train 5. Wily Castle 4. Dream Land 3. Pictochat 2 2. Magicant 1. Mute City
As for the returning stages, I'm pretty torn on them. There's some solid stages back, like Jungle Japes and Coerneria, as well as ones I'd rather be left behind like Brinstar and Mushroomy Kingdom. Distant Planet is surely the worst stage in the game, though.
At first the stage seemed a little bland to me, as well, until the EarthBound footage started up in the background. That's when I knew this stage was something special. And, of course, there's also the music. Best music in the game? You betcha! Then again, I have an EB bias.
What's the big appeal with Magicant? Seems kind of plain to me, though I only played it once so far.
It's impressively full of fanservice. Like, maybe the most in any Smash Bros. stage ever. Although it helps to be familiar with EB, but off the top of my head, there's the giant tomato from Magicant, Mobile Sprout, Flying Men, Dungeon Man, the Octo Statue (JPN version), and a ton of scenes playing in the background void from Mother 1 and 2. Both songs are really great too, especially Smiles and Tears.
I did love Earthbound but I guess I don't have the same connection to the series as some do. Upon playing more though I can definitely see the appeal of the stage, even if it isn't necessarily one of my favorites.
It seems for many of the stages anymore, I play on the ultimate mode (or whatever it's called). As despite the mode being flat and boring, it keeps the action close. That's a handy feature to have on a tiny screen!
3D World is so ridiculously colorful and charming. It's a moving stage yes... but it's still pretty fun to play on.
Magicant is a stage representing something I have no context for but still I love the aesthetic, the level design, and the background action. The Flying Man is great when he's on your side but he's a pain otherwise and could definitely be tweaked going forward. Still, this is an absolute favorite of mine.
Paper Mario is another fantastic stage. I love how they pulled from all different games in the series and the ship portion ALMOST makes me not miss the fact that Pirate Ship from Brawl isn't in this game.
Tortimer Island is an insta-fav because it makes great use of an Animal Crossing-related area. It's relevant to the recent handheld AC game and having Kapp'n show up is icing on the cake. It's a simple but effective stage.
Mute City is another one of my all-time favs in the new game. There's something so well done in it... maybe it's the sprite racing action or something but it looks splendid and the vehicles seem to battle like they might in the actual F-Zero game. It keeps for an action-packed stage with great music.
I also really like the 3D Land stage. The timing of the music and pace of the stage's movement is great.
I'd also like to mention...
Tomodachi Life - I like the concept of this stage's ever-changing apartment building. The vertical layout offers plenty of space, allowing for strategic and fun movement. It's also a pretty laid-back stage with a goofy vibe to it that I find appealing.
Gerudo Valley - This is one of my favorite places to battle. It's a spot-on recreation of a memorable environment from Ocarina of Time with a few neat hazards that keep you on your toes.
When it comes to stages I don't really have a favorite I have those I like and those I don't like. Currently I enjoy playing Gaur Plain and Arena Ferox but those are just because I loved X.C. and F.E.A. But on the bright side no stage is as bad as the worst from Brawl and Melee.