Depends. If they market DmC as a game more for casual gamers, then that would probably sell better just because it's a bigger market. However, they'd have to make sure DmC 2 is a really high quality product. Anyone looking at DmC can tell it has shoddy frames per second, texture pop-ins, and washed out graphics. It's also glitchy as hell. Since DmC/DMC doesn't have a massive fan base, if you want either game to sell outside of the established fan base, you need to make sure the game is really polished and has amazing marketing.
That said, If Devil May Cry 5 and DmC 2 have about the same amount of quality as their previous game, then DMC5 will sell better.