All mapper90 games was produced by some company, called "JY Conpany". All these carts have unique ID code like JY-xxx. Some of JY carts not mapper 90 games, but all mapper 90 games are JY. Earlier versions of 90 mapper now assigned as 91 mapper and used in some old pirate games like early "Mortal Kombat II" pirate version and "Dragon Ball Z - Super Butouden 2".

Here short list of known JY games:

"45-in-1 (JY-120A)" - contain full version "Super Mario World", "Popeye 2 - Travels in Persia"
"Aladdin - Return of Jaffar, The" - conversion to mapper 90 of "Lord of King, The"
"Aladdin" - well known SNES port of "Aladdin"
"China Rabbit Baby" - clone of "Mickey Mania 7"
"Donkey Kong Country 4" - SNES port
"Final Fight 3" - SNES(?) port
"Mickey Mania 7" - SNES port
"Mike Tyson's Punch-Out!!" - conversion to mapper 90
"Mortal Kombat 2" - MK1-MK2 port
"Mortal Kombat II Special"
"Mortal Kombat III Special"
"Mortal Kombat 3 - Special 56 Peoples" - variations of MK2-MK3 port
"Popeye 2 - Travels in Persia" - clone of "Aladdin"
"Power Rangers III" - fighting game
"Power Rangers IV" - beat-em-up game
"Shin Samurai Spirits 2 - Haoumaru Jigoku Hen" - fighting port
"Super Contra 3" - SNES port of "Contra Spirits"
"Super Mario World" - single game version, only 4 levels
"Tekken 2" - fighting port
"Tiny Toon Adentures 6" - "TinyToon Adventures" total conversion, GB port

Most of JY games have easter eggs inside, like wheird splash screen with some kind of "logo".
Look for "JY Easter egg" here: http://cah4e3.shedevr.org.ru/cheatsbase.php

Also it is known "King of Fighters 96, The" 768Kb version by "Hummer team" is JY too, reproduced to MMC3 alike board, but contain the same easter inside. And I'm pretty sure "Street Fighter Zero 2 '97" is Jy too, because it developed by the same "Hummer Team", but haven't easter inside and uses the same as "KOF96" MMC3 board. I need labels for these carts with JY code to proof it.

More info here: http://cah4e3.shedevr.org.ru/cartsbase.php

Enjoy.