Reasons:
Better graphics and sound
Alex Kidd
Shinobi
3D glasses
Complaints or counter arguments:
bad Controller design
the system did not have a good pack in game
The system was too "kiddy" (i refute that in the last section below)
No "Killer Apps" (once again Alex Kidd and later Sonic)
addressing the "kiddy console" argument"
The NES is by and far The OG of consoles, let me be clear: i am not knocking it, i am simply giving fair and honest reasons as to why it's competitor is in a league of it's own. You can argue that The rivalry is black and white and convince me of the wonders of Phantasy Star (and believe me i love it, in fact i have all 4 games thanks to Sonics Ultimate Genesis Collection and love them all).
The Master system has two things that the NES lacked or barely featured:
*Better Graphics: Show me A game that took full advantage of the NES's Palette and i will show you games that were better in every way
Nes: Super Mario Bros 3
Shadow of the Ninja
Contra (not Contra Force)
TMNT 1,2 and 3
Tetris
Sega Master System:
Phantasy Star
Alex Kidd in Miracle World
Shinobi
Afterburner
Sonic (late arrival but still counts)
Quantity vs Quality: The NES had Mario, the SMS had Alex Kidd but both had Gems, however, the Master Systems games were better in some areas and worse in others (Double Dragon's Hit detection, Sounds for Phantasy Star blew FF out of the water)
A few notable mentions:
T2: the arcade game (i will never EVER play T2 for NES ever again!)
Rambo III
Ghostbusters
Mickey Mouse in Castle of Illusion
Ghost's n goblins
Batman (among others)
NES:
Super mario bros 2 and 3
Contra and suoer contra
Batman returns
Batman
Tetris
Bram stokers Dracula (better graphics, sharper polygons)
etc
Do you agree with my reasoning? let me know in the comments
P.S I love the NES but lately, i feel my skill slipping. i was once able to beat the fencing segment of track and field 2 without error. now i can't. Gaming is like an erection: it gets harder with age lol