The best sf to me are Super T (I have been playing this game just recently and it rocks) and Hyper Fighting. I dislike 3rd Strike and the parry system. There is not character variety in this game, everyone plays pretty much in close range to be effective. Look at Necro for example, that guy could have been an extreme range Dhalsim type of character, however since the parry nullifies his attacks he HAS to play at close range to be effective....like 90% of the rooster in the game. And parry unballances everything, if you choose a slow character you are fucked up because your attacks are easier to parry.
ST and Hyper fighting are more ballanced in my opinion. In 3rd Strike if you choose a character that has a lower tier than you rival´s character, you are pretty much in disadvantage (the game has a very rigid Top tier) but in SF that is not case. Look at ST Honda and Bison. Bison is a top tier and Honda is a bottom guy, however he Honda is a bad matchup for Bison, he basically beats him for free. There are other examples as well.
As for Alpha, I don´t like it. If there is something I don´t like about 3rd Strike is the Genei Jin, and fact that everyone in Alpha a has genei jin here makes hate this game more than sf3. Fuck cc.