Also let me add to the OP the question: what is so great Amare Stoudemire? Sure, he jumps high and puts up nice numbers, but if he was even 1/2 the player Kevin Garnett is now, wouldn't he have found a way to make the Suns even close to a contender by now?
Sure, you can point to the fact that KG couldn't put it together until he came here; however, KG never had the surrounding cast Stoudemire has always had. KG had Sam Cassell, Latrell Sprewell and some scrubs and made it to the ECF. Stoudemire had 3-time MVP Steve Nash, Shaq, Grant Hill, and Jason Richardson and couldn't even make the playoffs last year.
Sure, he might play better with this group in Boston, but he's been able to do very little with a fairly talented group in Phoenix. And let's also not forget that he's had his share of leg woes and also had lots of miles on his legs at a young age since he was drafted straight out of high school.