Thats my claim and I'm sticking to it. As evidence, simply play through his games. You will find some of the most spectacular attacking chess you will ever see. Especially the games between himself and Mikhail Tal. There 2 attacking masters go at it, with Nezh ending up with a plus score against the Wizard from Latvia.
Of course I'm not his only fan, with Andrew Soltis giving Nezhmetdinov's 1958 game against Lev Polugaevsky his vote for the best game ever. There is even a blog in his memory , mrnezhmetdinov.blogspot.com.
And while the Polugaevsky - Nezhmetdinov game gets GM Soltis's vote, his 1962 game against Chernikov is one of my all time favourites, containing one of the greatest moves ever seen at the chessboard.
Nezhmetdinov,R - Chernikov [B35]
Rostov Rostov, 1962
1.e4 c5 2.Nf3 Nc6 3.d4 cxd4 4.Nxd4 g6 5.Nc3 Bg7 6.Be3 Nf6 7.Bc4 0-0 8.Bb3 Ng4 9.Qxg4 Nxd4 10.Qh4 Qa5 11.0-0 Bf6 (D) Up until this game this variation was considered an easy way to draw with Black. White has some difficulty in finding a good square for the queen, as Qf4/g3 runs into Qxc3 followed by Ne2+, and Qg4/h3 is met by d5. That leaves Qh6 when Bg7 forces a repetition. So Chernikov figured that Nezhmetdinov was looking for a day off with a quick draw. But in this position Nezhmetdinov began to think and think. His confused opponent wandered around the hall for 40 minutes waiting for his opponent to offer the draw. That was until ...
12.Qxf6!! Ne2+ 13.Nxe2 exf6 14.Nc3 Re8 15.Nd5 Re6 16.Bd4 Kg7 17.Rad1 d6 18.Rd3 Bd7 19.Rf3 Bb5 20.Bc3 Qd8 21.Nxf6 Be2 22.Nxh7+ Kg8 23.Rh3 Re5 24.f4 Bxf1 25.Kxf1 Rc8 26.Bd4 b5 27.Ng5 Rc7 28.Bxf7+ Rxf7 29.Rh8+ Kxh8 30.Nxf7+ Kh7 31.Nxd8 Rxe4 32.Nc6 Rxf4+ 33.Ke2 1-0