Bernie makes some decent points, but I think Sam's ceiling is higher than he does. Maybe not Peyton Manning level, but certainly higher than Phil Simms level.
On the flip side, I do wonder how some of these other elite QB's would have done in their first 4 years if they were throwing to the same caliber of WR's as Sam has been. When Manning came into the league, the Colts already had Marvin Harrison at one spot and Faulk in the backfield. And a couple of years later, he had Reggie Wayne on the other side, with Edgerrin James behind him. How would he have done if he had a Steven Jackson on the downside of his career while his best WR's were Danny Amendola and Brandon Gibson? There is only so much you can do to 'elevate' those guys.
Or take Warner. Obviously I love the guy, but when he finally got his opportunity he came into a situation where he had a cache of weapons that would land him on a government watch list these days - Bruce, Holt, Faulk, Proehl, Hakim ... good lord. And please don't say Warner elevated these guys ... they had already had that ability. Bruce had monster number in 1995 with Mark Rypien and Chris Miller as his QB's, and excellent numbers again with Tony Banks throwing to him.
Let's see what Sam can do with good weapons before we set his ceiling.