[quote=@Ignacious]
Time to begin my search...
[Hider][img]http://i.imgur.com/o4RGnIk.jpg[/img][/hider]
[/quote]

Just go back and forth to the first route and starting town. You will literally never find Entei anywhere other than the first route, even though he appears other places. Every single time I've seen him, in Gold, Crystal, HG, and SS, he's been on that route in the first patch of grass. You can track him on the gear map.