Haha, I remember before even playing Real Bout, I was super into Alpha (1 and 2 at the time). I bought Real Bout 2 for my AES before even playing it because it looked like it was like Alpha's art style. I love the hell out of RB2, but the magic from Alpha/Zero1, and then especially 2, just puts it over the top for me. My vote goes to Alpha/Zero.
I love both, however, but the feeling I had when I first played Alpha. Wow.
With that said, I think that Real Bout has cooler characters and MUCH better music. But, it's not everything.
Spike