The 3D in LG TV is far better than Cinema, depending on projector of course. There are only a handful of cinemas that would be able to beat the sharpness of LG's 3D.
Yes, it'll convert 2D content to 3D, you'll get the feeling of depth, but it won't be nearly as good as a movie shot in 3D. A lot of the movies aren't even shot in 3D, but mastered in 3D instead, there's a difference here. I'd say based on what I've seen, that movies that weren't shot in 3D, but mastered in 3D, is about equal to the 2D to 3D converting done in LG's TV's.
I advise you to buy a 4k 3D TV, as long as it's got HDMI 2.0a, and HDCP 2.2 specs listed and confirmed, otherwise you won't get any picture when you want to watch native 4k content. Forget about Netflix, or any streaming source, they don't even come remotely close to the quality and clarity of a blu-ray disc. Once there are native 4k blu-rays on the market, then make your decision whether or not you want or need 4k, because you will pay a premium for the player, and you will pay a premium for the 4k blu-ray discs.
Another problem apart from HDMI and HDCP; is the fact that a 4k TV (3840 * 2160 pixels) using Passive 3D, is going to show you "half" the vertical resolution, but please ignore every single one that says that Passive 3D can't look better than Active, as that's completely false. I've tested and used 3D since the beginning to today. There are several Active 3D TV's that look worse than Passive 3D, and that won't change anytime soon. You need a refresh rate of 240 Hz so that you get 120 Hz for each eye, in order to get rid of ghosting on an Active 3D set, where as on Passive 3D's, there's no flicker and no sync problems. If you decide to buy Active 3D TV, then buy a 240 Hz TV also.
I will say this though, majority of people have no clue what they're talking about when they say 3D. A movie shot in 3D, gives you the 3D depth similar to how a poster is built from the scratch, meaning you get a foreground, midground, and background, all throughout.
Watching content in 3D, movies should be your only concern. Gaming too, if you're into that. The problem is that there's no native 4k content anywhere on the market, yet, and you will pay a premium like I've been saying, but is going to be worth it, definitely. I still think it's too early to invest in 4k though, and I won't change my mind until the manufacturers have stopped the war between what features they want, and what standards will apply with the new format, muddy waters right now. The manufacturers aren't going to sell a lot of TV's because they're 4k, but because they're pushing features such as HDR, which improves perceived color, and brightness of the TV's, making them look more natural.
If you like 3D movies at the cinema, then definitely buy a 3D TV, that's all I can say. 1080p will be more than enough, Passive or Active, whichever you prefer. Passive is cheaper and can look identical to Active, so don't judge based on the technology, but test results.
All the best!
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