Online is good if you don't take it serious. Just play for fun. If you only want pro games then yes, WiFi sucks donkeyballs. Freezy can't beat me but sometimes online lag screws me over all the time. SF4 has the same problem only yes. Wow I have a lagspike while I do my Dictator long link combo, resulting in eating Tiger Uppercut.
Conclusion, fighting games and online never go great. Frame advantage, which is sometimes a measly 2-3 frames are sometimes nullified because your input lags behind. They are there just for fun.