ASoIaF: Randyll Tarly is apparently the best battlefield tactician, although Tywin Lannister and Robert Baratheon are also apparently good. Robb Stark is probably the best strategist we encounter in the books, outmaneuvering and outplanning the considerably more experienced Tywin Lannister several times

WoT: The five great captains are all supposedly badass - Rodel Ituralde, Pedron Niall, Agelmar Jagad, Gareth Bryne and Davram Bashere, whilst Mat Cauthon is probably now on a par with them and Lan is also reportedly pretty good. We haven't actually seen much from Bashere, Bryne and Jagad, but certainly Niall's grasp of strategy was impressive and Ituralde's mastery of both grand strategy and battlefield tactics in fighting the Seanchan is extremely impressive, so I'd rank him as the best we've seen so far in the WoT world.