I'm 3.5 metres from my TV. I had a 42" Samsung plasma and it was good size-wise - that's the smallest I would go at that distance. I then gave the 42" to mum and bought a 50" Pioneer and really like it from that distance. I've had it for about a year and a half and never wished I would have gone bigger.
For LCDs Sony and Samsung are the leaders at the moment, and for plasmas Panasonic and Samsung. Sony and Samsung use the same LCD panels, but different circuitry, so they are pretty close to each other.
TV specs are sometimes totally useless, and published contrast ratios are definitely utterly useless as there is no standardisation of measurement - one TV can be 1,500,000:1 and another can be 2000:1 and they will be identical. Some review sites provide real contrast ratios.
Most videophiles will agree that of more importance is the black levels that the TVs can achieve (which does affect contrast ratio of course). Plasmas have historically been ahead but LCDs have closed the gap a fair bit. LCDs still have off-axis problems so the further you get from central viewing, the more washed out blacks will get. There are a lot of additional things that are important as well though.
If I were forced to buy a TV now I would go a plasma, and probably lean towards a Samsung even though Panasonic are often championed as "the best".
If you are willing to wait there are new Panasonics which should finally achieve a picture that can compete with the old Pioneer Kuros. If it were me, that's definitely what I'd do. Not sure when these new TVs come out, it could be a year or so but it might only be a few months.
It is a good idea to get to a store where they have lots of TVs on display. Bear in mind their settings will be awful so it's pretty much impossible to compare colour and sharpness, but it should give you an idea about whether you prefer LCD or plasma pictures at least (if they allow you to tweak settings, generally put them in a "Movie" mode, adjust sharpness to zero, turn colour down, turn contrast down, and turn brightness down until you reach the point where absolute blacks stop decreasing in brightness). And since there is so much to what makes a decent TV, if you feel like reading reviews this site is the best I've found:
www.hdtvtest.co.uk. Processing lag is also important for gaming and they talk about that in most of their reviews, especially if it's especially terrible. I drag consoles into the store to test when buying TVs.