I daresay there's a lot of licensing issues with these things, Contra and Gradius are Nintendo ports so there would be legal issues with their games depending what platforms they were received on, it would get messy legally.

Konami owns both Gradius and Contra, so they can do whatever they wish with them. Konami did do some licensed stuff, like the Ninja Turtles games, Bucky O'Hare, Wild West Cowboys of Moo Mesa, GI Joe arcade, and a few others, but a majority of Konami games were original Konami IP's (Capcom did a ton of licensed stuff, so a lot of their stuff can't simply be part of compilations, but they still did 2 great Capcom arcade compilations). Nintendo owns absolutely nothing of Gradius or Contra, because both were arcade games originally, and there have been Gradius and Contra games on other consoles (especially Gradius, which was on the Sharp X68000, PC Engine, PS1, PS2, PSP, and the Sega Saturn). Nintendo basically owns nothing Konami has put out, the only thing that Konami couldn't legally port to anything else would be the DDR game with Mario and friends in it.

Yes sir