Tito Shivan Mar 19 @ 3:20pm
GTA IV showing video cards with over 2GB as under spec
https://support.rockstargames.com/hc/en-us/articles/200145206-Issues-with-GTA-IV-showing-video-cards-with-over-2GB-as-under-spec

You can workaround the issue by adding the following to the game launch options
(Right Click -> Properties -> Set Launch Options)
-nomemrestrict -norestrictions