One modder prepared an interesting project – he ported the Quake 4 shooter to the Quake 2 engine.
The author of TheMrBenpulido – recreated all the levels from Quake 4 in Quake 2, using the graphic elements of the “deuce”. Models of enemies and the sounds of shooting from the fourth part were also used. Music added from Quake 3, and the interface is updated.
Here are some Screenshots of the mods:
The mod is available for free at the link, but to enable it you will need Kmquake2 or the basic version of Quake 2 with an unofficial patch 3.24.