It may be obvious, but the best looking one you can afford.

When I bought my TV 3 or so years ago, I wanted a full HD (1080) plasma because of the contrast between colours and blacks were great, 51" because of the size of the room, basic (non-smart) tv because I was hooking up a home theater PC to it and won't require internet, YT, etc and finally it had to be full HD. I ended up buying a Samsung PS51E531A6M for JBs.

I would recommend, depending on what type of TV you watch (movies, sport, cartoons, gaming), it will influence what type of TV you might buy, however I think with most new LCD/LED technologies, these now rival plasma's contrast benchmarks. I am not even sure if they still developing plasmas?

I would then ask the question if you want a smart TV or a plain old dumb one. If you have a game console, this may do all the same things as a smart TV, however I think using a controller may get tedious. I think you may be able to plug a keyboard via USB (maybe wireless) into a console and it would work. Has anyone tried this?

When comparing TVs, I like to look at; nature documentaries because of the vibrant colours they can have, dark dramas to compare blacks and greys and action movies to compare how clear (lack of blur) they are (thinking of Transformers).

Lastly, I would try and buy a TV with the highest refresh rate that is measured is Hertz (Hz). This is essentially how many frames are shown in 1 second (Frames Per Second - fps). Most games these days (on console) are 30fps and are now pushing into 60fps territory. PC rigs can exceed 100fps and is one of the reasons people tend to play games on PC.

Below are some reference text taken from some of my favourite tech based websites;
Best TV 2015: what TV should you buy?: Buying a new TV - what you need to know | TechRadar
Buying a TV in 2015? Here Are 11 Things You Should Know
HD TV 2015 Buying Guide: Sony, LG, Samsung And Panasonic | Lifehacker Australia
TV Buying Guide 2015 - CNET

Good luck in finding a good TV that suits your needs.