I didn't know much yesterday but your comment sent me into a rabbit hole so here we go : The impressive quality of j2me games is because they ran using java through a middle layer called java 2 platform, micro edition (j2me) that allowed programmer to not care about individual platforms/phones but just use the phones capabilities through APis. This didn't really work that well because there was all kind of contraints. I vaguely remember reading John carmack rant about developing the doom rpg serie for different resolutions and the sound api being garbage.

Old Nokia phones ran on serie 20. It didn't run java games. It's successor the serie 30 had the capability to run java games but only the serie 40 made all phone run java games. The serie 60 aka SymbianOS was the real deal and kept receiving updated until it's death in 2012.

Sony ericsson phones like the k800i ran the java platform 7 (each generation of phones ran a newer version, the last bein java platform 8) directly on an Rtos (real time operating systems)

Lots of the oldest ones were binaries for really ancient embedded operating systems