Well, I guess LCDs tend to have brighter colours, which might be an advantage for gamers, but I can't really think of that much else, apart from the fact that there are more LCDs with the full HD (1080p) resolution than there are full HD plasmas. But 1080p plasmas do exist, and one in particular - Panasonic's amazing 42PZ70 - is extremely good value for money... I have seen it online today for just £888. I know this is a little bit over your budget but it is well worth it.
But back to your question, I believe that plasmas are better for both movies and games. This is because they handle motion much better, they have much more realistic colours, true deep blacks unlike LCDs which can only go as far as darkish grey and I reckon that plasmas just have a more attractive picture with smoother edges, and a more cinematic picture than LCDs. And the only advantages that LCDs might have over plasma for gaming, and other viewing aswell, is their ability to display a slightly brighter picture during the day when it's light, and slightly brighter colours - though this is at the cost of true blacks and colour depth and realism. Oh yeah, LCDs tend to be lighter so they are easier to take round your mate's house for some sort of deathmatch or whatever you gamers get up to these days.
As for the lifetime thing, I am pretty sure that both plasma and LCD are pretty similar in this regard. It's a myth that either type of flatscreen "only last for two years because the gas / liquid runs out, and to refill costs more than the tv itself" - this is rubbish, absolute rubbish. I believe these tvs' lifespan are roughly 60,000 hours - that means if you had your tv switched on constantly, 24 hours a day, 7 days a week, it would last for mover 7 years, which I reckon is pretty good.