CasualGames that require litttle-to-no pre-knowledge of gameplay, easily played by new gamers and old gamers.
Examples: Bejeweled, Peggle, Super Mario Bros, I Spy: Haunted Mansion, Animal Crossing
Easily Paired With: Hidden object games, Puzzles, Adventure Games, "Secret Box"
Games that will be difficult to play if you don't play often, but become a lot easier once you get into them.
Examples: Halo, Call of Duty, Pokemon
Easily Paired With: Most simple genres
Games that require knowledge of the genre or a long history of playing games to be good at. Very hard to newcomers. Interesting to note that some Common games can have Hardcore presences when played online, much like how you can play Chess on a casual or master level.
Examples: Resident Evil 5, Borderlands 2
Easily Paired With: Most complex genres
Games that require a lot of time to be good at. Even if you're used to playing hardcore games, you will need much time and patience to be good at this.
Examples: Nethack, The Binding of Isaac, Civillization 5
Easily Paired With: Strategy games, Roguelikes, Simulations
Games that at first appearance look hardcore, but soon prove themselves to be comparable to Master-difficulty games. Of importance is that failure here is expected, and often encouraged. It does not simply take time and luck to get good at; you require an insane amount of skill, and may simply be the wrong person to play this game.
Examples: Super Meat Boy, Dark Souls, Marvel vs. Capcom 3, I Wanna Be The Guy
Easily Paired With: Platformers, Fighters