As has been said Riker is overlooked.. he's easily one of the best officers Starfleet has and only recently got his own ship. He's very smart, quick wits and he rarely plays by the book and likes to improvise (to great success). That makes him a brilliant tactician and given a bit more time will easily fill the shoes of Picard and maybe make his own impression on Starfleet.
Agreed. I would have voted for Riker.
Out of the current list my vote went to Kirk, with Sisko as a close second.
TNG 'Rascals' Riker is a good tactician?
I would pick Archer. With an inferior ship, he outmatched klingons at least thrice, he found the solution to the xindi crisis, etc.
Kirk's achievements were far too often based on luck - because the writer said so (for example, star trek 11; TWOK Khan unable to understand space has 3 dimensions). And, in TWOK, he made a 'Rascals' worthy mistake - more than large enough to eliminate him from the competition.
Picard - beyond the Picard maneuver, he has little to show for; only the basics. A one trick pony does not a good tactician make.
Sisko mastered the fundamentals - but that's it. His achievements were based on the fire-power of his ship, not his tactics.
Janeway had technobabble and not much else.