Not sure if some of these are rare but i have....

NES

Mario 

Tetris

Duck hunt!

SNES
Donkey kong country
Super street fighter 2
Star fox
Lion king
Super Mario World

Sega Genesis 

Streets of rage 1-3

Shinobi 3

Sonic 1-3, sonic and knuckles, sonic 3d blast

N64
Rouge squadron
Zelda Oot and MM
Golden eye

PS1
Suikoden 1 and 2
Megaman legends 1 and 2
FF7,8,9
Chrono Cross
Lunar 1 and 2
Metal gear solid.

GC
MGS twin snakes
Resident evil 0,1,2

Ps2
Ico

Wont bother with most GC, Ps2 and up since im not to sure whats considered rare for them.

hmmm, Dark Cloud 2 I'd say, I think it's quite rare. Price mainly $160 as of now and up I think it was. I use to have rare NES games, SNES, N64, PSOne, PS2 & GC games. But having a brother that will sell anything you have and don't use or trade. You tend to lose all collected rare games despite it being yours not his smh. Dude stole my damn Dark Cloud 2 I had since release 2 years back because I didn't play it that year like I do yearly. Sold my PS2 and Dark Cloud 2 game together for $20 f***ing bucks. Had to buy back my game this year, found a guy who was tryina make some extra coin and was willing to get it off for $35. But going into the future now I'll have alot of rare games seeing I love niche games these days and I don't have him taking my stuff no more lol. Sorry for the story. Maybe, CTR, Crash 3, spyro3 or FFIX? ohh well lol

Things from my collection I'm particularly proud of.

Zelda (Game & Watch)
Gyromite (with ROB and all accessories)
Super Mario RPG: Legend of the Seven Stars
Super Metroid (COMPLETE)
Mega Man X
Paper Mario (COMPLETE)
The Legend Of Zelda: Majora's Mask (Collector's Edition) (COMPLETE)
Starcraft 64
Paper Mario: The Thousand Year Door (COMPLETE)
Dance Dance Revolution: Mario Mix (COMPLETE)
The Legend Of Zelda: Ocarina of Time/Master Quest (COMPLETE)
The Legend Of Zelda: Collector's Edition (COMPLETE)
Mega Man Anniversary Collection (GCN) (COMPLETE)
Metal Gear Solid: The Twin Snakes (COMPLETE)
Baiten Kaitos: Eternal Wings and the Lost Ocean (COMPLETE)
Super Mario All-Stars: Limited Edition (COMPLETE)
The Legend Of Zelda: Skyward Sword (Collector's Edition) (COMPLETE)
Metroid Prime Trilogy (COMPLETE)
Fire Emblem: Radiant Dawn (COMPLETE)
The Last Story (Collector's Edition) (COMPLETE)
Xenoblade Chronicles (COMPLETE)
Bravely Default (Collector's Edition) (COMPLETE)

Ok thx for clearing that up for me. was wondering why it was so expensive but now I see that the players choice version is much cheaper

Also, Melee has multiple versions where they fixed bugs and left in more fun cheat stuff. The first release is the one with more cheat codes and options in the Debug menu. While 1.02 PC version has less exploits and options.

I don't own that many, just kameo and the first viva pinata.

Most rare games came out for nintendo systems or the original xbox, I was on the Sega side of things.

:P

SEGA has lots of rare titles on their systems.
If you got Panzer Dragoon Saga, Snatcher or Megaman Wily Wars, each of them is worth hundreds of dollars.

Rarest title I have is Bubble Bobble 2 on NES. Routinely goes for around $200 for just the cart, complete is usually 100-200 more.

First that comes to mind, especially after reading OP, is that I have Metroid Prime Trilogy as well. Got it on the first day they put it on the shelf in Best Buy. I've finished Prime 1, but still have not completed Echoes, and have yet to start Corruption. It kind of got pushed to the back of my mind after I began having difficulties with Echoes and became reliant upon walkthroughs. I was probably too impatient. I haven't touched it in a year or so... but I'll get around to it eventually