Not intrinsic value, we're talking resale. I was looking on Amazon and noticed some games I either got as gifts or didn't really pay that much for are really valuable now, so without further ado:

Lord of the Rings Battle For Middle Earth: Anthology, got this as a gift, now it's worth well over $100 on Amazon and ebay. Pretty amazing since I always thought it was a good not great game.
Xenoblade: Better or worse Gamestop had to reprint the game, which before was easily worth over $80, and more if you had the art book like I do.
For a little while there it seemed like Tales of Symphonia just kept climbing in value, before dropping like a rock in water recently, weird.
Metroid Prime Trilogy, in the condition I have with the original metal box and plastic sleeve can get somewhere around $70, which is pretty cool since it was a gift.

Wow, that's not a very impressive list, then again I churned for hours whether or not to spend the money on Chaser earlier. Well hopefully somebody else has something more interesting...

While some of these that I own in this list may be worth a lot, their scarcity is quite notable:

-Jazz Jackrabbit CD-ROM
-Tyrian
-The Elder Scrolls II: Daggerfall (Only in jewel case with front and back inserts)
-Commander Keen Goodbye Galaxy boxed collection
-Realms of Chaos
-Duke Nukem Kill-A-Ton Collection complete in box
-Intelligent Qube
-I.Q. Final
-I.Q. Remix+
-Powerslave for the PSX
-Wing Commander Deluxe Edition
-Silpheed for DOS
-The Complete Ultima VII
-System Shock CD-Rom
-System Shock 2 (Only in jewel case again)
-SIlent Hill
-Silent Hill 2 PC
-Complete Blood Collection (Not the One Whole Unit collection, but the base game and expansions included separately)
-The Elder Scrolls III: Morrowind Game of the Year Edition (Have seen the physical release become a bit more rare as the years go by)
-어쩐지 좋은 일이 생길 것 같은 저녁 1, 2 (Eojjeonji Joheun Il-i Saenggil Geot Gateun Jeonyeok 1 & 2) (Bundle pack of two obscure Korean beat-em-ups for DOS and Windows respectively)
-Deadly Premonition Xbox 360 (It's actually become kind of expensive in the secondhand market)
-Einhander

Whoa, I never thought I'd see actual Korean on this site, that's pretty freaky to me, for some reason. Good list, by the way.

Just looking, I think I could get a good penny or two for my X-Wing collection. It cost me a bundle to get and that was 10 years ago. Of course, I wouldn't sell them and I plan to be buried with them so the question is moot to begin with.

too lazy to list anything or look up the value online so here

http://www.gamefaqs.com/users/Mr+Crispy/games

don't think I have anything too valuable.

If it was in mint condition, it would be my copy of Digimon World 2003 for the PS1.
It's listed for an unbelievable 129.99£ on Amazon.

My favorite single player game:

Tug of war with the cyclops.

From first what comes to mind, I have following games, which probably have very high resale values:

Faery Tale Adventures II
Final Fantasy VII 1st PC port (no DRM outside CD-check, but it has tons of compatibility issues)
Final Fantasy VIII 1st PC port (no DRM outside CD-check, with Chocobo mini-game)
Hexplore
Icarus
Dungeon Siege I and II with all expansions
Demise: Rise of Ku'tan (without DRM AFAIR)
Wizards and Warriors

Lunar and Lunar II for PSX (they are considered rare)

Small off-topic, I hope there is chance to see Wizards and Warriors on GOG. Ever since WinXP this game refused to run properly and it is decent game along the lines of Might and Magic/Wizardry. Same wishes for Hexplore, very "lite" Action RPG but it was very unusual game for its time (and also has big compatibility issues with newer OS).

Didn't look at all of them, but you have one awesome collection there, I also have the collector's edition of Bravely Default and the first print of Project X Zone. I also noticed the rating you gave SRT:OG2, how? I love that game, to each his own, but was there anything in particular that was just bad about it? Oh, and you sir, have a far superior DS collection to mine, I tip my hat to you! (Helmet, being Animal Mother and all.) You don't really expect me to believe THAT was just a DOS game do you? I just watched some gameplay, that's another foreign language game for me to always want and never have. There's a store around where I live where the first two Lunar games are on sale for somewhere upward of $70 each, pretty cool indeed.

- Blood(One Unit Whole Blood) in an unopened jewel case sealed it the original plastic. Not for sale anywhere last time I checked so I imagine it is VERY valuable. And this version is the uncensored U.S. version. Not some censored special edition garbage. When I have the money, I'm going to find a way to preserve it for all eternity in a special vault.

All the other games I have that are not digital are used and not worth much.

I don't have any sealed, mint-condition packaged games, but I think I could still get some decent cash for these:

- Grim Fandango;
- Legacy of Kain: Defiance Collector's Edition;
- XIII Collector's Edition;
- Loom;
- Day of the Tentacle;
- Ikaruga (GCN);
- Terranigma (SNES);
- The Legend of Zelda: Twilight Princess (GCN) -- as it is quite rare;
- Nox (maybe I'm mistaking sentimental for resale value? I don't think it's that common a game to find boxed and working);

Oddly enough, I wouldn't actually sell any of these games (well, maybe XIII), so maybe I was just thinking of more than just monetary figures. :-P

Original boxed copies of Fallout 1 and 2, BG2 ,PST, IWD 1 & 2, Sacred 2 CE

The three major ones in my collection are Conker's Bad Fur Day (N64, cart only), MOTHER 1 + 2 (GBA, complete) and Klonoa: Door to Phantomile (PS1, complete with Point Blank demo). I adore all three games and am very happy to have them in my collection.

I also have Fast Striker and Gunlord on the Dreamcast too, which tend to go for high prices, though they're often reprinted and sold on Play-Asia.

The most valuable one I have is probably Megaman 7 for the SNES, which is currently going for $150 used on Amazon. I have a bunch of other Super Nintendo games that are expensive given their age, too, like Chrono Trigger (currently $90 used) and Breath of Fire 2 (currently 60 used). Oh, and Fire Emblem: Path of Radiance and Fire Emblem: Radiant Dawn, which are $65 and $75 used right now. Also, Majora's Mask collector's edition with the cool hologram cartridge, which seems to be selling for anywhere from $40 to $65.

Incidentally, the least valuable game I have is one I expected to be way more expensive when I looked it up: James Bond 007 for the Game Boy. Probably the best Bond game ever made (better and Bond-ier than even Goldeneye), and it's selling on Amazon for a penny. Sad.