I just came across an interesting article on Chessbase dated April, 2013 in which the authors attempted to compare how well players in the 2013 Candidates Tournament matched up against Houdini 1.5a at a 20-ply search depth in an attempt to measure the quality of their play.
What was most interesting to me was the scores of the World Champions:
How did they compare to players in the Candidates Tournament? Carlsen (3.9), Grischuk (4.5) and Kramanik (5.1) all had higher ratings than past champions. Aronoan, Svidler, Ivanchuk and Gelfand were roughly on the same level as Kasparov, Petrosian and Fischer while Radjabov tied with Smyslov.
One might be surprised to find Tahl ahead of Botvinnik, but the truth is, you don't get to be World Champion without being proficient at all phases of the game; Tahl knew how to play positional chess and endings; you just didn't see a lot of those games. Botvinnik knew a thing or two about tactics, too. Play over the great Tahl vs. Botvinnik world championship match games and you'll see them both hammering away at each other by any and all means available: openings, strategic play, tactics, endings.