In my experience there are two situations where wolf is not necessarily in an advantageous position:
1. When the stage layout works against wolf effectively covering space with his attacks such that it locks down and covers opponents options OR the opponents coverage and movement options are complimented more by the stage layout than are yours (ie. Martha vs wolf on yoshis story I've found to be very hard since math can easily cover entire platforms with quick attacks, and the small stage size gives wolf little leeway in maneuvering).
2. When the blast zone distances allow the opponent a means of killing more quickly and efficiently than you can kill them (ie. Peach vs wolf on dream land: peach can survive much longer because of far blast zone and great recovery, whereas wolf is edge guarded extremely quickly, swaying the MY toasts peach since she will outlive wolf a lot of the time)
obviously this is very MU dependent, but thats really how most stage selection decisions are. ive found that stages like skyloft and metal cavern can often work against wolf with the slanted stages since they really work against the coverage that his attacks provide. wolf works extremely well with platforms and medium to big stages like battlefield and dreamland unless the opponent falls into either of the categories above. against marth ive found it best to avoid small stages (YS, FoD, green hill zone, etc..) because of his huge grab range, great DD, and large disjointed spacing. you will want more space to outmaneuver and avoid his large ranged attacks. marth is obviously only one character, but that process in general is how i usually determine my stages.