I have been looking around for these again and can't find them anywhere other than 2nd hand on ebay and some of them can be quite expensive.
Lucasarts always said the reason that they will not release any of the older games again is that there were written for dos and would not run on the more recent O/S, however with Dosbox this wouldn't be a problem.

From the FAQ, which is stickied at the top of this forum:
Will you be adding *insert game/publisher here* to the GOG library?
GOG does not release specific information on prospective games or publishers until they already have agreements in place. They will not comment on who or what they are trying to get, only what they do have. Check the site's main page for news on what is coming soon, it gets updated every Thursday
Why are some highly requested games, such as System Shock 2, not being added to the catalogue?
GOG tries to get every game they can, but sometimes it is a difficult process to find the correct rights holder, secure permissions to sell the game, get gold masters of the games, modify as necessary to make the game work on modern OSes, etc. It's not that GOG is intentionally not adding a highly requested game, its that they can't unless or until they can meet all those requirements. That certainly doesn't mean you shouldn't keep requesting and voting for games, though. The more interest we can show, the more "ammunition" GOG has to bring to rights holders to convince them to allow their games to become part of the GOG library.
As a new user, I suggest you read the FAQ before creating any new threads. Other than that, welcome to GOG :-)

Unfortunately 2nd hand is usually your only choice.
Oh and vote for them on the wishlist, keep on supporting GOG and pray that Lucasarts joins in the GOG party.

There's quite a few voting for them already so lets hope so.

well knights of the old republic would be cool to plus some of the old x wing title might be good to!
p.s for the x wing titles would you need a joystick to play them?

I never had a joystick when I played Xwing, TIE fighter and Xwing vs TIE fighter. I much preferred using the keyboard, no idea if I'd still think the same way these days!

The notion that LucasArts would ever put their old games out is laughable. They sit on all their franchises, then go after anyone who dares to upload them on their abandonware website.
However, I've heard some rumors that the new Indiana Jones Wii game may come with Indiana Jones and The Fate of Atlantis as a bonus, so maybe they're softening up to the idea...

The only reasoning I can think of (and this applies to EA also), is that they can prevent other companies using those IPs, and also they can force people to buy new games rather than older cheaper ones.

Which new LucasArts game would I buy in lieu of Loom or Day Of The Tentacle, then?

Actually, that was a joke. LucasArts hasn't made any of those games since they decided to make only crappy Star Wars games from then on, since all the Star Wars geeks would buy them regardless of how badly they sucked. It's one of the greatest tragedies in gaming history: The Day The World's Greatest Adventure Game Developer Decided To Stop Making Adventure Games.
[EDIT] I see you seem to have spotted that afterwards ;-)

Guybrush: If you kill me... there wouldn’t be any more Monkey Island sequels. Then, if you kill me everyone will forget you.
LeChuck: Forget me? I’m the dead zombie pirate LeChuck! No one will forget me!
Guybrush: Do you remember Bobbin Threadbare?
LeChuck: Er… no.
Guybrush: Exactly.
And in response to your question, I would recommend "Star Wars: A Battery Farmed Golden Goose"

hey, WWE, what kind of chance is there these games might end up on GOG.com ?
WWE responds!

[EDIT] I see you seem to have spotted that afterwards ;-)
Yeah, i spotted it eventually, needed some sleep.
They did make some good games afterwards just not adventures. Dark Forces 1&2, KOTOR 1&2 (if you like RPGS), X.Wing & Tie Fighter, i even liked Mercenaries, still mad they didn't release it for the PC though.
It is a shame that they only churn out for the most part, crap games for their 2 franchises (star wars & indy).

NO CHANCE IN HELL!