Id like to personally point out that BO2 actually did a dang good job of the leveling system this time.
1. Some of the best perks, like ghost, are saved until VERY last. Hell, Ghost is 55.
2. You can keep 1 item after you prestige permanently after each prestige. Play through once, you get to keep your favorite item.
3. Prestige mode helps with the 'fairness' aspect. Someone whos been playing 6 months more is going to have the exact same classes after they prestige as the newbie has.
4. Gun unlocks do not reset every prestige, and they even have incentives to hamstring yourself. Example: To get Gold camo for most guns, you have to get kills without perks/attachments. Yeah. Also, there is a special camo, diamond camo, that you can only get after you unlock all the gold camos for a class. Keeps things mixed up.
So yeah... leveling up is done right in BO2... AC3 though is a different story.