Easy
1) The World Warrior
2) Suicidal creatures
3) Green Hill Zone
4) Communist legos
5) Simian Land
6) Nod Prevails!
7) More Devils

Natalya has died
9) The Shores of Hell
10) Green pipes
11) Finish Him!
12) Tactical espionage adventure
13) Doop de doop de doop doooo
14) Beastly difficult
15) The Golden Power (series title not just one game)
Medium
1) 8 bit adventure, precursor to Bust A Move
2) 2 lizards
3) Limit Break!
4) Alien rush
5) Watch those banana skins
6) Ringworld
7) Can you find 8 red coins?

Whats with this weird fog?
9) Amiga Rollerball
10) You found a nailgun
11) Into the Dark World
12) M-M-MONSTER KILLL
13) Hairless fence opening
14) 4 player glove
15) Cannonball Ferrari
Hard:
1) Hail to the king baby
2) Where the hearth is, in space
3) Torture land
4) Russian
5) Gymnastic crypt finder
6) Megablast
7) Sega's medieval brawler

12 bosses, some horse riding and not much else
9) Pre Skyblivion
10) Feeling Deadly
11) Normal Football
12) Original space terror
13) Hi Yah!
14) Kick flip spin
15) Jet fighter arcade machine