Possible spoiler alert!
Ive read a lot that the game goes down hill one the aliens come into it, I personally don't think so ... I mean i spent the first part of the game fighting the Koreans, Going it with a silenced weapon, Cloaked & mostly trying to take them out one by one without being seen whenever possible.
Then the aliens come, At first i was trying to do the same thing against the aliens as i was against the Koreans, After a few fails i realized that's not the way to take the little buggers ... Oh no, With the aliens im now finding myself having to just run at them with all guns blazing, Get in as close and possible & fill them with lead until dead lol .... This works, Its fun.
Oh BTW, two mods ive found work well with both games & make them look stunning:
Crysis:- Silents High Resolution Foliage & Crysis CCC V1.31.
Warhead:- Rygel High-Res Texture mod & Warhead CCC v3.00.
(Warhead actually looks better than Crysis in my imo, Just had a quick look at the first lvl of Warhead to make sure then mods where working, Gonna save Warhead for after i complete Crysis)