I'm going to go with true AND false. It's true in the sense that Aaron Rodgers has to prove that he can perform under pressure and "when it matters." Ultimately, some people think Brady is better than Manning because of the SB ring count of 3 to 1. But like one of the answerers said earlier, since when has winning SBs become a team game? Personally, Manning played OK in the SB game vs. the Saints and it wasn't his fault.
In an ideal world, I'd say Rodgers just needs a solid performance in the SB to be considered as one of the top 3-5 QBs. Win or lose, if it's not his fault, then how should that affect people's perception towards him?
In reality, he'll need to win AND play well to considered a top 3-5 QB. People say that not only do you need to play well under pressure, but really good QBs like Brady and Manning can compensate for their team's shortcomings in other areas and bail them out. Personally, I've seen Manning do this a lot, but not so much Brady.
Btw, I think the Top 5 QBs are: Manning, Brady, Rodgers, Brees, Rivers. Vick has all the tools, but he has to prove that he can replicate next year. Roethlisberger is in this debate too.