if you read these :
then you will see that the aim in ssbb is completely different than a game like mortal kombat or street fighters.
1. n00bs will be able to play the game but will not be able to get good like someone who plays alot more can, it requires good timing and strategy and is really hard to get good at, the fighting is alot deeper than any other fighter and the replay value is amazing. but this is a good thing because you can play this game with anyone that comes over even if they are a "noob".
2. i started off with melee which i bout about 3 months ago and played it and loved it so i can be better when ssbb comes out. but you CAN dive right in to ssbb without playing the other 2 ssb's, it will just take a while to get used to, but it will be fine because there isnt a deep story line or anything like that.
3.i answered this above .
hopefully i answered your questions :S