JMb, perhaps. But if we did that, Fischer would also suffer. His 2789 rating was based on five events (the Candidates tournament, and matches against Taimanov, Larsen, Petrosian, and Spassky). As we know, ratings based on matches rather than tournaments can often be misleading.
Radjabov had a +2780 rating from November, 2011 through April, 2013.
How long a span would you like to see, and with what parameters?
Just saying.
@SmyslovFan, it's probably more useful to compare ratings over a span of time, not just the peak rating. Calling Radjabov the 8th best player of all time is pretty ridiculous.