I started with a Commodore 64. I had experience with IBM PC XTs early in high school and later PS2s but I liked my Commodore 64 so much better than those. My first "PC" was a 486 from Gateway. Doom, Doom 2, Mechwarrior 2, NASCAR, X-Wing, Tie Fighter, Heretic, Descent...those are the games I remember the most from that time.
I wanted to upgrade around the Pentium MMX era but was a poor college student at the time. I managed to upgrade a little later with an early Pentium II. X-Wing vs. Tie Fighter, X-Wing Alliance (I really liked this series of games), Baldur's Gate...those are the games I remember most from my P2 days. I probably would have gone with AMD had I been building my own systems at the time. I would with my next PC which was Duron based which would fairly quickly be upgraded to an Athlon XP.