-Color correction: i have no idea wether it's too saturated or too intense
-3D-text: there are two major text signs in the beginning who rotate horizontally while fading. As you can see, it's just plain text in 3D-mode. Any idea how to add depth to that text within After effects or with a plug in?
-Slow mo: the background of those opening text blocks are blue flames slowed down. Problem is it's kinda laggy. Any idea how to do a smooth slow motion with no lag?
Color correction is a matter of personal taste. I think you did OK but I'd probably drive the shadows a little more toward teal or blue and give a bit more of a knee to the highlights. It's a little warm for a shoot 'um up for me. The first shot is close to the look that is used for most films like this, the latter scenes have much warmer shadows. There's also a decidely different look to several locations. Change in color mean change in the theme or mood of the scene. Warm = Romance, love, puppies and kittens, family and babies. Cool = lust, fear, danger, death.
The easiest way to make 3D text layers have a little depth is to stack copies up using an expression so that each copy is 1 pixel deeper in z space, then parent the layers together or move a camera.
The slow mo may be improved by using pixel motion rather than frame blending. You could also try using Twixtor. Slowing down footage just with software has it's limits and the lack of detail in your flames makes this even more difficult. It would help if we knew what technique you used for the slowmo and how the original footage was shot. For future reference, it's easier to slow down interlaced footage (most of the time) than to slow down progressive footage.
One last comment, I'd do some more work on the muzzle flashes. Soften them up, try some different blending modes, and make them a lot more subtle. It's way too obvious that they are VFX.
For CC, get Magic Bullet Looks if you can, or try to imitate the look from other movies of the genre (as Rick said, high contrasts and a little blue or cyan in the shadows is more suited for shooter movies). Also, don't be affraid to go more orange with the skin tones, mimics the film look much better than the pale pink tones you have now (personally I think they look too much like Betacam), and I'd go with a tonal contrast between the skin and the background (the blockbuster look - 0:10 or 0:35 are almost there). Now, you're the director so you decide what's best for you, I only recounted what I'm usually asked for.
Besides the muzzles, you need to refine the glow on the big screen at 0:22. That type of glow goes with holograms better, for a screen it should be a very subtle glow with long ray lengths. And bleed it over the character's cutout, it's too crisp.
For 3D text you can go with Rick's method, but you can't control countours and bevels very well (actually, at all). I'd go with Shapeshifter AE from mettle.com.
For slowmo, Twixtor is the de facto plugin, but the results depend a lot on your footage. The safer bet would be to buy some stock footage that already looks good and you just need to change the hue.