I've been on a SMS kick the past few years, picked up db-elec FM thingy that renewed my interest. I had a Master System next to my NES bitd, but when I got the PBC, I traded of the console and kept only r-type, Golden Axe and P.Star.
Since then, I've bought and sold a good chunk of titles, but ended up with keeping these:
Action Fighter <- Found this to be more enjoyable than Bomber Raid
Alex Kidd in miracle world <- Mainly for it being the mascot
California Games <- Surfing is my jam and has FM support
Choplifter <- it's way hard, but slick parallax
Double Dragon <- everyone heralds it for being 2p
Enduro Racer <- I really enjoy this one, simple but fun
Golden Axe <- love the graphic style
Golvellius <- Music is tops
Hang-on/Astro Warrior <- My original pack-in, LOVE Hang-on
Phantasy Star <- my first console RPG, f*ck Final Fantasy!
R-type <- SO GOOD! Reason to keep the console.
Rambo First Blood part II <- Recent pick up, I enjoy it.
Rampage <- FM tunes do it justice. Might be repetitive but I keep coming back to it.
Rastan <- great 8-bit port albeit shorter levels
Time Soldiers <- I'm a big Ikari Warriors fan form the arcade, TS was always a runner up.