I'll go against the grain and say yes.
What if he played 5 more years with stellar numbers but didn't have a Cup? He would have the gaudy numbers some seem to want, but without the most coveted prize.
So what's more important - padding one's individual stats through longevity (in rather meaningless regular season games), or winning the Cup, which had eluded Boston for nearly 4 decades?
And as Thomas' Conn Smythe attests, that Cup win doesn't happen without him.
Plus I think Thomas' longevity gets underestimated. He was a 4 time All Star, won two Vezinas, a Jennings, in addition to a Conne Smythe and Stanley Cup. Mix in his rags-to-riches journeyman story, and I believe he's earned it.
I've been fans of players who put up HOF numbers but never won the big one - Craig Biggio, Jeff Bagwell. And though he has a Cup as a backup, Rask has had two chances in the Finals. Because Thomas won the Cup, that puts him over the top.