It really depends on the games. Modern Warefare 2 for example, 7900xtx outperforms 4090 in every resolution. While in fortnite the 4090 outperforms the 7900xtx even more.

@ 4k gaming then 4090 on average is /much/ better than the 7900xtx, but looking at 1080/1440p that lead deminishes alot.

edit: At the end of the day tho its all too damn expensive now.