Confused

Wondering why theres a list of "playable games" are these games considered to be finished with tweaking builds or what? Haven't got a game to run on my emulator yet tried creating a disk image playing around with the file and did the same with another game also tried downloading one of the games just to see if i could get it to work that way still nothing. What puzzles me is this has been out for years is it true that only a handful of games are still able to be run by it? if so why? Why cant one emulator made to emulate the same system's games play all the games.

Because the emulator it's far from complete. That's why it's v0.0.0.9 (pre-alpha). Many functions are missing and there are a lot of inaccuracies.
Also, newer builds can break games that worked before and make games that didn't work before work.
Simpler games that make use of simpler functions that are already implemented are the ones who usually work. Still, they don't work Perfectly as you can see in the log while playing them.
Games that are Half-Playable and have simple bugs to fix are sometimes looked at by a developer that tests the game and fix the inaccuracies in the emulation that's causing the game not to be Playable. Example: Check the topic for After Burner Climax and Resogun.