I don't buy this at all.
Your first premise is that Amare will still be "tearing it up" in 3-4 years. This guy lives off of his legs, not his skills, and those legs have taken a big beating so far. Amare missed an entire season with a microfracture surgery, and unless he changes/expands his game, there will be more of that.
Garnett, while he has definitely spent some time up above the rim, is a skilled player. The only thing he doesn't do as well as Stoudamire is score inside, though he likely could do that if he didn't pass and shoot from the outside as well as he does.
Garnett is in great physical condition, he's a smart basketball player with every skill there is, and he plays defense. Garnett may be six years older, but judging on what I've seen, Amare is a much better bet for the glue factory in four years than Garnett is.
Second, you're going to criticize Garnett for not going to the Finals in twelve seasons even though you know good and well he's been surrounded by garbage most of that time? The one year he had good help (not great) around him, Minny won 57 games and advanced to the WCF. Amare's been on a loaded team in 05 and 07 and he couldn't get any futher than Garnett did.
I think many on the pro-Amare side are a little too impressed with his dunks, because Garnett is better than Amare at literally everything else.