I'm not denying the ATG status of that Galle knock, it was a freaking awesome knock for sure.
But to me he never looked very comfortable against an in-form Muralitharan, he looked suspicious against his doosra when Murali was at his best. He dominated the waning master for sure. But remember Muralitharan didn't keep Sehwag in his list of 10 best batsmen he bowled to.
There is a different point about Sehwag that I want to point out here. His natural style of play is way too aggressive than all other batsmen I've seen, which is good. And that's the reason when he gets going, it might seem like he's the maestro at work. Take this in contrast to the likes of Miandad, Azhar, Mahela or Sanga - who are technically brilliant against spin. These are kinds of players who are equally comfortable while defending, manouvering and attacking spin. Comparing spin-play of Sehwag against these players is like comparing pace-play of Ponting against, say, Sunil Gavaskar. Due to the natural aggressive style of play, Ponting is definitely a more dominating player of pace than Sunny, but does that make him a better player of pace than Sunny?
On the other hand, I can never forget the way Lara dominated both Warne and Muralitharan at their respective primes. I don't think anyone else came even close to achieving that. Even Tendulkar, who dominated Warne probably more than Lara throughout was merely good against Murali and a little suspect against Saqlain. Not only Warne and Muralitharan are the two best spinners of this generation by far, their bowling style is so very different from each other that dominating both of them 'in their respective primes' puts Lara on a different plane than anyone else for my money.