Quick Conversions
Here are some games, along with their Japanese and American names. You can use an emulator or console forced to Japanese hardware settings to play the original game (or at least most of the original game) without applying an IPS patch.

Game Gear

Bare Knuckle / Streets of Rage
Bare Knuckle II / Streets of Rage 2

Mega Drive / Genesis

Axis / Final Zone
Bare Knuckle / Streets of Rage
Bare Knuckle II / Streets of Rage 2
(Special instructions on this page)
Daimakaimura / Ghouls N' Ghosts
Peacock King 2 / Mystic Defender
Ryuko No Ken / Art of Fighting
Tatsujin / Truxton
Thunder Force II MD / Thunder Force II
V-5 / Grind Stormer

The names in the US version of Gaires were changed to silly, bad-cartoon-sounding things. Run it on Japanese settings, and all will be well, though.

Most of the Sonic the Hedgehog games will be partially restored (mostly, you may notice Tails referred to as Miles). There is an IPS patch available that will turn the American Sonic the Hedgehog to the Japanese version, which has no Japanese text but does have extra parallax and graphics that were missing from the U.S. game.

Another good one is the game Mercs, which was actually Senjo No Ookami II. It may be of interest to you that the first Senjo No Ookami was called Commando in the U.S., so Mercs is in essence Commando II.