@illuminosopher: I have played Mortal Kombat, Street Fighter, Dead or Alive, Virtua Fighter etc. as single player experiences. I don't mind playing against the computer. Is their enough to Smash Bros. gameplay wise for a person to keep going against the computer?
It's so much different than any of the games you mention, I would say if one of the major things you enjoy about the games you listed is learning complex combos you will not find that here however you will find a lot more variety in terms of gameplay I honestly think for me personally that smash offers a lot more gameplay for single player than any of the games you mention.
I should also mention that on the 23rd of this month at 3:00 pm PT Nintendo will be having a Smash Bros video event that will showcase 50 new things about smash that will probably be worth watching. http://www.nintendo.com/nintendo-direct/10-23-2014/
@carino: gamepads battery life isn't that bad, I have only had it start to die twice during 5 hour monster hunter gaming sessions at which point I just plugged it into its charger and continued using it while it charged.
There isn't much depth too mario kart it's just a real fun game, smash bros I think has a fair amount of depth and usally tons of stuff to unlock but I would say both are at their peak when played with others.