What a tough question to answer, stretching all the way back to Atari 2600 for me.
I think I'll pick No Mercy/Virtual Wrestling Pro 2 on the N64. Possibly thousands of hours both solo and competitive at a friends with some incredible round robin tournaments with up to five participants. Just amazing Create A Wrestler and one of my handful of favorite gameplay mechanics ever. Also we were paying during the exciting days of pro wrestling so we had that enthusing us as well.