I had a TI-83+ in high school and a TI-89 in university. I found the Z80 calculators (ie the TI-83+ etc) had way more availability for games than the 68k (ie TI-89). I think it was simply the Z80 had a bigger user base. (When I was in high school, you could use a Z80 calculator for exams but not the 68ks because the 68ks could do symbolic algebra.)
I'm a little out of the loop now, but
ticalc.org was the big community back in the day.
Joe Wingbermuehle came out with his ION shell and a bunch of assembly games. Then the guys at
Detached Solutions came out with the MirageOS shell and a few more games.
After that I move on to the TI-89 and kind of lost track of the community.
For me, Diamonds by Joe Wingbermuehle was the pinnacle of calculator gaming. I repeatedly played that game just trying to shave a second or two off my high score.