What makes Tatsunoko Vs. Capcom: Ultimate All-Stars such a pleasure to play isn't the mechanics, it's the cast. It's like a good issue of Marvel Comics' What If? What if the super heroes of Marvel took on the combatants of Street Fighter? What if most famous of Capcom's games were to fight some of the most memorable characters from Tatsunoko's animations? And in this case it's the cast that sells this game.
You can buy Tatsunoko Vs. Capcom because it's a solid enough fighter, or because it expands the fighting genre for the Wii. But you're going to love it because of the cast.