I would think Dune over C&C. Dune really defined the RTS with resource gathering and unit production.

I guess Dune deserves more credit, but I always thought the orignal was pretty bad. D 2000 was okay but I always felt C&C perfected (at that time) the RTS and helped make the genre as popular as it became, thus the yardstick moniker.

Elite, the first huge (8 galaxies) space combat/trading game, a decade before the likes of X-Wing/TIE Fighter.

Chaos Strikes Back. Dungeon Master on steroids and then some. Perfected the real time blobber ganre, making every subsequent effort (Eye of the Beholdet, Lands of Lore et al) an anticlimax in comparison, IMO.

Ultima Underworld. The first true 3D game with a "living" (although small) world with a physics engine.

Doom. The game that really created the FPS genre.

Thief: the Dark Project. The first true stealth game and the first to use "3D" Sound. Still unsurpassed. A game like Splinter Cell doesn't even reach up to the toenail clippings of the Thief games.

Tenchu pips it to the post with over 1/2 year - first released in February '98, while Thief in November '98....

Oh...I've never heard about Tenchu.
But I see on Mobygames that it's 3rd person, so it can't have the same immersion or reliance on hearing (and not just sight) as the Thief games.

Tenchu: Stealth Assasins

Moby Games - http://www.mobygames.com/game/tenchu-stealth-assassins
Wikipedia - http://en.wikipedia.org/wiki/Tenchu

In my view, the most enjoyable stealth games series ever made... but I am a bit strange...

For me, one of the benchmarks for games that are based on a non-videogame franchise is Star Trek: 25th Anniversary and its sequel Judgment Rites. They are primarily point & click adventure games, but also includes dialogue options that allows you have Kirk give different responses to the people he meets. There are several self-contained episodes in each game, and there is ship-to-ship combat that works decently in my opinion. The best part of these games is that they feel like actual episodes of the original series, so it is a real treat for me as a Star Trek fan.

Honorable mention goes to TIE Fighter as well, since it is a pretty good game and has you playing someone who isn't a part of the Rebel Alliance. The best games based on a franchise should keep true to the spirit of what it is based on, but also expands upon it in some way. :)

Too bad they are 3rd person. If they were 1st person they might have been worth trying on an emulator.
Amazingly enough for a Japanese game the characters actually look like people and not anime versions of 8 year old girls in skimpy clothing.

try them, they are the first 3D stealth games. There is nothing like being a Ninja, jumping from roof to roof and silently assassinate all mobs. The grappling hook is it prime selling point.

I did; I just played it. I suppose not necessarily a now, but in was absolutely a yardstick in the 90s. Anyway, it was the first thing I thought of :P

Also, the oldest 'yardstick' today, would have to be rogue, given the surge of 'roguelikes' recently; although, I'm sure most people have never played the actual game, and know of it just by the term 'roguelike'.

Tetris. It made gaming more mainstream and accesible to non gamers. It also made portable gaming a viable option.

I generally hold third person shooters up to Gears of War.

Primordia is a new yardstick of mine for adventure games.

I also hold some strategy games up to Civ.

Rereading the OP, I will agree with you 100%. It is hard to differentiate between yard stick games and the game that defined a genre. I think Dune 2000 defined the genre, but C&C is the one that perfected it. Does Starcraft challenge C&C's "yardstick" though. Would most current RTS be compared to SC or are they still being compared to C&C?