Some website I think you should browse

MAME Team - the best arcade emulator, with sources! This is how the wonderful world must be!
Scott Tunstall's Robotron disassembly
Scott Tunstall's Galaxian disassembly
Reverse Engineering a Classic Arcade Game: Super Street Fighter 2X
Reverse Engineering Street Fighter 2 THE WORLD WARRIOR
The Pacman Dossier
Test Pacman Ghosts' AI
Kroah's Game Reverse Engineering Forum
[Tutorial] Reverse Engineering Step by Step in Klonoa Game
Reddit REGames (lot of newbies post but you could find a gem)