Shinon is the best and most fitting. I like Skrimir's, though honestly, I expected a much louder voice for him and every time I read his lines, I automatically imagine a louder, more fiery voice in my head. But despite all that, it's a good voice and very fitting, like the growls of a lion (sort of like Mordecai's, as someone else here said so a long time ago).
Zelgius and Dheginsea suffer a little from the acting standpoint, but they both had excellent voices, something I would expect. Same goes for Tibarn...except the "Keep up with me if you can!" line sounded a bit too ^_^ to me. Like suddenly Tibarn was all cheerful and gay. Ranulf was cool, Jason Adkins is kind of more fitting as older Ike and the rest range from average to bad (narrator notwithstanding).
The generics were all great though.
MY EYES
OHH THE GENERAL'S GONNA LOOOOOVE THIS <--- This guy in particular had a very rich and seductive voice. I bet voice acting is his part-time job and he's really a pimp.