Just as in other genres there are two well respected developers that produce the majoirty of titles. Capcom are the best known for the [Street Fighter]? series that although is only up too Street Fighter III has still managed to spawn dozens of versions. The first [Street Fighter]? game is quite mediocre, it wasn't until Street Fighter II and Street Fighter II CE that the franchise really became popular. Since then subsequent incarnations have seen the roster of fighters evolve and swell, leaving at times, just the main two characters, Ryu and Ken from the original Street Fighter II line up.
Contrasting with Capcoms approach is SEGAs AM2? developers, the Virtua Fighter series has seen just three and a bit versions since its inception in (year?). Each new installment brings with it years of carefully refined mechanics, style and gameplay and is always a big event.