Karmapilots,
If you are serious about gaming i would say that a decent Panasonic plasma like the V20 would be a good option but it maxes out at 50 inches. Most LEDs and LCDs have significant input lag which more or less worsens with each year's release. Most Samsungs are considered extemely laggy. The Sony EX700 and Samsung C8000 are just about ok in this area but serious gamers can still complain about it though.
If you like the picture quality of plasmas there is also the 63 inch Samsung C7000 3D plasma((about 217K), 58 inch C6500(130-135k) the 60 inch LG PK950(1.10k-1.50k). These should also meet your movie and gaming needs. With gaming though there are the usual chances of temporary image retention on all these and there can be some visible phosphor trailing to extremely sensitive folks.
For movies too i think plasmas are a better option considering motion . But you could compensate some of the motion problems on an LED/LCD by adjusting the distance to the TV and by buying a Samsung which allows you to adjust dejudder/blur modes hence allowing you to improve motion resolution without giving a video feel when using 100hz/200hz technologies (though this was best demonstrated on their last year's sets)
It may be confusing with so many options around but at 55 inches i don't think there is much to choose between the 7 series, 8 series LEDs and the 7 series LCDs. The plasmas from LG and Samsung are worth considering with the 950 being just sheer VFM and good reviews.....you could also consider the LG 9500 which is a fully backlit solution better in many ways than the Samsungs but with banding issues and a reflective screen.
Its not simple to make a choice without considering all the pros and cons of each technology(plasmas on one hand, CCFL,Full backlit and edge lit LED LCDs on the other) and please take time to find out as much as you can before making a decision. Spend time visiting as as many brandshops as possible for displays and playing around with TVs. I can recommend two showrooms based on personal experience where people have been very helpful in the past. There is a Samsung showroom on the same road which has pretty much all Samsung models on show but you might end up leaving there with a very bad taste
LG Showroom-Rajajinagar
Panasonic-Rajajinagar
At the end of it my personal choice for movies and gaming though would still be a plasma preferably Panasonic which sadly has limited sizes in its line up