KOEI Math: Shin Sangokumusou (n) = Dynasty Warriors (n)+1
 

This is a big LOL, here's nice proof:
You can safely rename the games:
Dynasty Warriors 4 Hyper = Shin Sangokumusou 3 Hyper
Dynasty Warriors 5 = Shin Sangokumusou 4 Special
"iamtrouble" :D

Good to know as I already thought it strange that covers did not match...

But there is one strange thing, there is a game called Shin Sangokumusou 3 @ GCW but checking the wiki there is no pc version available... so the wiki is not complete or it has a wrong name...

i think they had several versions of shin sangokumusou 3 - the hyper & the normal one (but dunno if it was relized on pcs)