The trailer for Sega Superstars Tennis, releasing next month for all current-gen systems, looks like a lot of fun. I've never played Mario's takes on this sport, but I imagine its characters were all able to perform the same maneuvers, just to different degrees (as in Mario Kart). By contrast, Sega's game confers unique abilities to each character, making it more reminscent of Technos' old Super Dodge Ball, which kept me awake until many a dawn.
Plus the variety of heroes who don't usually play together — Sonic, Aiai, Ulala, and someone from House of the Dead — warrants a look just for the sheer novelty of it.