I'm pretty sure you just have to take into consideration the general body of work. The average(s). So, going back to the Shaq in the 2000's thing, he was dominant for the first few years but started tailing off pretty hard in 2007. So maybe his last years of the decade dip what you might consider his contribution, but you're still getting a great player. 90's Shaq is better though because there is no tail-off and it didn't take him any time to get going when he got to the league either.
But yes, since it's a popularity contest, there's something to be said for the namesake. Mutombo isn't exactly an all-time great though, even considering his 90's stint (his best). And he was awesome too. This isn't an exact science, obviously (and especially since this is vote-based), but just put together the best team you can given the general parameters.
