This is a hard one without breaking it down by genres and/or SP vs MP, but if I was to truly narrow it down to a few franchises/titles, it'd be:
1. Quake(s) - first e-sport ever, also for me as a player
2. Fallouts - writing, atmosphere, complexity (especially first 2)
3. Deus Ex-es - ditto
4. Dead By Daylight - first async horror... despite all its flaws, it brought me lots of enjoyment... actually, it brought back excitement of multiplayer gaming for me, although I wouldn't recommend playing it too much, hehe
5. Gwent - I love CCGs and this one's the best, hands down
6. Mortal Kombats - loved it ever since I was a kid... not the best fighting game mechanics-wise, but there's just something about it overall that makes me love it more than SF or Tekken, for example
7. Need for Speeds - I love racing games and NFS has always maintained a good realism to arcade ratio
8. Starcrafts - I actually barely played it, but I watched the hell out of it as an e-sport