Megadrive version of Tatsujin. Why? Game is hard as balls but more manageable than the arcade version (or the thoroughly unfair PCE version). It's also a Sega conversion to boot so it's prety much perfect. I still play this game weekly
Thunderforce 3 MD version (bonus points for the 3D version and the CD audio Saurn version, avoid the AC/SFC version at all costs). Game is incredible, can be super hard on Maniac difficulty, had a bawler OST
Thunderforce 4/Lightning Force MD version (bonus points for the suuuuuuuuper expensive Saturn version and its cd audio). Game is downright beautiful, the best 16 bits era shmup (sorry PCE fans), had an insane soundtrack and incredible bosses
Turrican 2 Amiga version (super bonus points for the cery memorable and unique ST soundtrack which I love go death). The epitome of the Turrican games, all the other games pale compared to that one (including the Super NT exclusive Super Turrican DC). Chris Hulsbeck at his best, open ended levels full of secrets and exploration (despite the timer which should have been removed), incredible level design, enemy variety, fair and balanced difficulty, shmup levels (and very good ones at that). Dem graphics!!!
World of Warcraft : this game stole 600 days of my life over the past 14 years (yes, that's 600+ /played on my main). Incredible music, atmosphere, design, gameplay, lore, questing. Seeing the game evolve over the course of the main game and 7 expansions is just so good, so rewarding
TLDR :
Tatsujin Md
Thunderforce 3 MD
Thunderforce 4 MD
Turrican 2 Amiga
World of Warcraft