Aquanox Collection

Old but gold it meets here in my opinion the best.
Aquanox 1 is a nice game but the graphics are not exactly overwhelming, but this does not bother me.
Aquanox 2 is for me one of the best single-player shooter ever, especially since it has a damn good graphics for age.
In both cases, the gameplay is really good, the story in Aquanox 2 is captivating and the opponent is not too easy.