I played almost excusively on mobile back then (my parent's or sister's mobile, until I got big enough to get their phone as they switched)(that is how it should be imo).

snake game on feature phones

Clash of clans (when i left, third guardian was just added, and town hall 11/12 was the highest and I left around 9).

subway surfers (played it a lot)

paper toss (not that much, but i guess enough to remember)

hill climb racing (1 and 2) (i think i completed 1 completely)(completed in sense of bought all vehicles and maps) and 2 a little. I recently reinstalled them, and 2 is just not it anymore, 1 is still fun if played offline.

a lot of pokemon and rom hacks, for about 2-3 years

The Battle Network series! Although I played on emulator. You can imagine how happy I was when I heard of the legacy collection rerelease.

I got absolutely hooked on Sonic Mega Collection ( Mega Collection Plus is better because save states, but that's neither here nor there right now ) because my grandpa thought it was a game that me and my brothers would like. That game collection turned me into a huge Sonic fan.

Also, Crazy Taxi is an amazing time killer. First game I got when I got a Dreamcast for Christmas a couple years ago and it's real fun. Cannot vouch for any other version/port of the game, but it's a blast.