Oh dumbass you say?
The only thing GTA:3 and VC had in common was the engine, which is the same engine San Andreas used (it's called RenderWare). Are you going to tell me SA is a mod too? There goes your biggest argument.
VC had a new landscape (without the old one included) different vehicles, 3 times as many weapons, new vehicle types and classes, a different feel and color pallette, more radio, better radio...
In other words, despite you claiming that VC was simply GTA:3 modded, Vice City is better in every way, and whats more completely different in every way. It doesn't look or feel the same!
What makes SA not a mod then?