I was big on Robin Lopez and I still am. If you are expecting him to become a starting caliber center on 30 NBA rosters, you are going to be disappointed.
Lopez is exactly what the Suns needed, a back up C/PF who is athletic, can rebound, plays defense and blocks shots. Lopez is going to be a solid rotation guy at least.
He isnt his brother, but I think he has a lot of potential. You have to remember this guy is barely 19, is still developing his shot and mid range game, and he was in high school 2 years ago. Big men take time to develop, but Lopez is going to be at least a good rotation guy off the bench and I think he can be that this year.
As for McGee, he was all potential and nobody expected him to play this well this early. With that said, the Suns drafting him would have been a huge risk because they needed their #1 pick to come in and play minutes right away. Lopez, while still needing develoment, was ready to play a role right away.