Just pulled these from a London Bar Guide, apparently they all show NFL games. The second one seems the most similar to what you'd be used to in a sports bar. The last one sounds like a strip club to me, but there you go.
F3K
171 North End Road, W14
(020) 7603 6071
With 16 TV screens spread all around the premises and almost continuous coverage of football (be it Premier League, First Division, Scottish Premiership, Spanish League, Bundesliga, etc, etc) F3K (or the Famous Three Kings, as it is sometimes known) can quite accurately claim to be one of the top sports bars in town. If your idea of "being sporty" is getting sloshed whilst watching TV in West London then it'll be right up your alley.
Sports Café
80 Haymarket, SW1
(020) 7839 8300
Just as the Uffizi Gallery could be considered the art lover's ultimate destination, or the Bauhaus Archiv somewhere for fans of early 20th century architecture to revel in history, London's Sports Café must surely be one of the planets finest sports bars. This temple to skilful athleticism boasts 120 TVs, 3 bars and a dance floor. It is even open till 3am! With a menu featuring delights such as Foul Play, Souper Bowl and Power Play Satay, it's almost as inspiring as Jenson Button's new haircut.
Rainbow Sports Bar
72 Shoreditch High Street, E2
(020) 7739 2959
As well as boasting a couple of big TV screens (usually featuring boxing or American Football) this place has something none of the joints above can offer, namely naked women.