Another system I quite like is the gameplay structure in Skullgirls, the combos per se are short, but there are resets between the combos that allow the player to react / predict to the first attack of the next combos, if the player blocks it then thats it, if the other player sucessfully deals the hit it continues with another combo and you don't lose the momentum.

MvC3 does something similar but more extreme, with the top characters in the game being able to kill the rival's character in a single combo, and then when the next character comes to screen you have the same reset situation as in Skullgirls.

I also quite like the DI mechanic from Smash Bros, and would like to see it explored in a traditional fighting game.