I made a graphic for stage legality.

The 7 stages with question marks are being debated quite a bit right now.
IMO Pokemon Stadium 2 is fine now. No more tripping on Ice, everyone falls faster now for Air, no more infinites on Ground, and the conveyor belts move slower on Electric.
Wuhu Island has an OHKO glitch which hopefully will get fixed in a later patch.
Kongo Jungle and Pilotwings MIGHT be okay but also might be severely campable.
Mushroom Kingdom and Mario Kart 8 stages would have been okay but they have a bunch of hazards like Nabbit, falling icicles, rising spikes, damaging hard wall ceilings, and shy guy karts.
Norfair I dunno someone said it was debatable in Brawl but I don't think anyone actually like it lol.
Even without those we have at least 10 good stages. Duck Hunt is probably leaning closer to Neutral so we have 6 neutral stages and 4 transformation-type counter picks. So much better than the 3DS' stagelist like holy shit :V
For doubles/3v3/4v4 the stages that are banned just because they're too big are fine, namely Big Battlefield and Windy Hill
and Hyrule Temple :V