My top 5 QB's all time would have to go as followed:
1. Tom Brady (yeah he has guys around him, but if having guys around you meant auto-championship than their should be alot more guy's with rings)
2. Joe Montana (4 superbowls just about seals it)
3. Peyton Manning (He has every skill you could want in QB, and is probably the most intelligent QB of all-time)
4. John Elway (Probably the most athletic QB that can still throw Hall-of-fame-like passes)
5. Brett Favre (people may dis-agree, but he is one of the best leaders of all-time, and he has one of the best arms of all time)
Troy Aikman is good, but he had the NFL's all-time rusher, and he just doesn't pass my test for all-time greatness. Terry Bradshaw was decent, but he had a lower career rating than Tim Couch, 2 HOF recievers, and one of the best defenses of all time.
Dan Marino was also great, but he never won a superbowl, so their is no way he get's my vote.
As for Roethlisberger, he may not be the prettiest player you've ever seen, but he is a flat out winner. He makes plays without a good o-line, his running backs were banged up all season, and he will go down as an arguable top 5 QB. I would not be surprised if he ends his career with at least 4 superbowl rings, and I can all but gaurantee he'll make it back to the big game this upcoming season.