This has come up a few times, so I'll just repeat the basics of what I've said before: in the ballpark of Sonic. Not EXACTLY Sonic, but that general type, smug, confident, wisecracking kind of thing. But not overly femmy, or super masculine or gruff or anything. Just a smug, slightly athletic sounding early 20 something, typical hero type. I think the sort of voice Spiderman often has (not Peter, Spiderman) might also be a good point of reference.
But also, I mean...he sounds like what you imagine him sounding like. That's the whole point of text. It plays out in your head and your brain fills that in.