the way i see it, its about consistancy. ryu is VERY consistant in the damage he deals, since his shoryukens and whirlwind kicks arent based on multiple hits, ken and akuma often dont deal much damage consistantly because their specials are mostly multi hitting, and if you dont get all the hits, (which happens very often) you do shit for damage.
In the end its like this Ryu= consistant amount of damage, ken and akuma= damage fluctuates from much less, to much more than that of ryus, depending on how well you play your round.
The differences besides hit count in specials are as listen below:
ken:
Three different, mostly usefull, hcf special normals, hcf mk, hcf hk, and of course… hcf lk.
Flop kick, not always used in high leve play for its… uhh, lets say predictability, it comes out a little slow, but thats NOT to say it has no use.
also noteworthy is that kens j.mk is a little different from the other shotos, its better for cross-ups.
ryu:
Hop kick, not so great but… you can use it here and there.
red fireball, hmm, its pretty usefull for stopping advancements on those who like to jump in, knocks down up close only though, and is not usefull in cc’s like akumas because it only does one hit (weak…)
His s.rh is a little bit different. at a higher angle and pretty good as anti air if you predict a jump-in but dont want to risk throwing a whiffed dp :S.
Akuma: More of an A groove character because of his ability to NOT waste an activation, lk hurricane, activate is TOO good, you can pull out the cc any time, and just lk hurricane to the corner where you do 400 damage for every red fireball you throw before the meter runs out.
His moves link in REALLY weird ways, you can do two light hurricanes one after the other, sweep into hurricane, dp out of MANY situations.
Demon flip, not so often used outside of his CC because of its… speed. another reason why akuma was made for A.
Air fireball-not what it used to be, 'nuff said.
a few more comments on super differences:
Ken deserves more for his qcfx2+p super 
Shoryureppa isnt so great, though it works good as a level 2 cancel, and you can combo into it from many jumpins… it seems to come out hella slow, and is very counterable if you DONT combo into it.
Ryu - GAH! Shinshoryuken does GODLY DAMAGE, too bad it has less range than a THROW. Super hurricane is too good, Great for that infinite level one in s groove, and if it gets blocked, EVERYONE trys to hit you after it, soo… immediately do shinku hadoken, hah hah, ive won matches with this alot. - note, dont use level three super hurricane unless you are 100% sure you are going to hit. Its always good to use level2 for reasons mentioned above.
I dont play akuma so i dont want to give any advice on his super.
