Ken or Akuma both amazingly cool characters, and to add I have mastered raging demon perfectly, well not at a arcade but on the snes to the ps2 I can do easily..
If it was the old Street Fighters, I would say Ryu since its all balanced character for close and long range combat with special moves that are fast to use. In the old days, my firends and I played cheap and had fireball duels till one of us messes up and get hit lol. The 2 seconds delay for Guile's sonicboom was too slow and no match for the hadoken. Altho Ryu and Ken were the same back then, I still prefer Ryu, even still now in the new Street Fighters cause he is still a well balanced character.
lol thats some in depth analysis into your favorite street fighter character Guile's sonicboom is annoying if your playing someone who knows how to time their combos well... but Ryu is probably my favorite char too
