The games here are
Final Fantasy VII (1997) vs Final Fantasy VIII (1999)
Parasite Eve (1998) vs Parasite Eve 2 (1999)
Resident Evil 2 (1998) vs Resident Evil 3 (1999)
(You could place Parasite Eve between FFVII and FFVIII since it came out between the two and was used to prototype some of the tech for FFVIII)
The leap in quality with the human character models is especially impressive. Look at Sephiroth's beautiful visage here and just think that Square went from that to feeling like their animation was convincing enough to carry an entire sci-fi drama movie with a realistic human cast in less than 5 years
spoiler
Then of course you had Oddworld Inhabitants who came right out the gate with movie quality CGI. Their characters all being fish-faced aliens instead of humans probably helped
The Tekken games on PS1 are like a self-contained model of this. The first one is like eugh, and the third one is like aw fuck yeah boyee
How could I forget about Tekken, possibly the best example to illustrate the point I was trying to make here
Check out the eldritch horror of Nina's sexy hair toss in Tekken 2's intro (around 44 seconds in)
and then we recreated it with real time rendering 20 years later with TressFX and Hairworks