Pretty good show. Prince is still the best by the proverbial country mile (I've elsewhere recommended that the NFL should just make Prince their steady), followed by U2 who were great at the country-still-in-shock-after-9/11 Superbowl in 2002, but M's the best of everyone else.
One other general thought: the show put M. back into perspective. On the one hand, yes, M. faces a problem: she's spawned generations of fast-hybridizing, dance-pop/mediaste imitators, and those hordes do threaten to make further output from her redundant, or to force her into the past. (Bowie faced a particularly galling version of this problem in the early 1980s, when he was confronted with hundreds of fast-moving young acts, assiduously mining out every open seam from every part of his catalogue and image-history. Imitation is sincerest flattery but it can kill the imitated host!) On the other hand, M. really is central to the sort of spectacle that pop has largely become. The Superbowl show demonstrated this by being both a version of the sort of performance that M. has done since the mid '80s, and also strikingly similar to much of what passes for state of the art pop music performance.
Update: I'm pretty sure that Madonna's big entrance/first look was supposed to recreate Liz Taylor's entry into Rome in Cleopatra (1963), but it actually felt more like Julianne Moore's dream sequence Maud Lebowski: