>>714046996
HD Collection is just a port of the first 3 games. 3 has some wonky text display on Steam for some reason. I'm pretty sure that the largest thing that you might point to is the HD Collection has more crisp graphics which some people think look worse because of the PS2-era graphics that a lower resolution can accommodate for.
The only gameplay difference is that 3 is the Special Edition which is just DMC3 but with more stuff in it.