Commander Genius
Commander Genius aka CloneKeenPlus is an engine which interprets Commander Keen 1-3 (Vorticons Series).

Yea yea, and it can be played without having the original version.

Modern warfare 2 in 2D. Here is a video.

Lord of Ultima
It's available now and free to play.

Why dost thee post such heresy, Avatar??? D:

To inform the people of such heresy! of course...

Is it any good?

*name *job *bye *inform

Dungeon Crawl Stone Soup
DCSS .6
Version 0.6 just came out and it is solid fun.

Can we list Flash games? If so, here are some Flash adventure games I thought were decent:
Ex Mortis [url=]http://www.newgrounds.com/portal/view/189227[/url]
Ex Mortis 2 [url=]http://www.newgrounds.com/portal/view/303832[/url]
Daymare Town series [url=]http://www.pastelportal.com/stories/dmt/[/url]
Something Amiss series [url=]http://somethingamiss.com/[/url]
Submachine series [url=]http://www.submachineworld.com/[/url]
Synapsis [url=]http://www.addictinggames.com/synapsis.html[/url]
Tipping Point series [url=]http://www.tippingpointgame.com/[/url]
Of course, there's also the Chzo Mythos series. Even the special editions are now free to download:
[url=]http://www.fullyramblomatic.com/games.htm[/url]
A lot of interactive fiction games, including the original Zork, are available here:
[url=]http://www.ifiction.org/[/url]
Free remakes of King's Quest I and II, and Quest for Glory II, are available from AGDI:
[url=]http://www.agdinteractive.com/games/games.html[/url]
Finally, a free remake of King's Quest III is available from Infamous Adventures:
[url=]http://www.infamous-adventures.com/kq3/[/url]

All your links go to Exmortis.

I fixed all the links for you. You have to put the URL inside the first tag, like so:
(url=[url=http://www.theurlgoeshere.com)The]http://www.theurlgoeshere.com)The[/url] text the link should show goes here(/url)
Just substitute square brackets for the round ones. You can of course also use the URL as the text to show, but you have to put the URL inside the first tag. Otherwise, all subsequent links you post (in that post) will link to the first URL.

free RTS games:
Spring: 1944 1.07
Kernel Panic 4.0
War Evolution 1.7
These are based on the open source Spring engine.

Oops, thanks for letting me know.
Thanks for the help!