I'm not sure if have mentioned this before on these boards, but one game that gave me a lot of ideas to use in Traveller, and a general atmospheric "feel" of things, is Independence War (or I-War). It's a space sim from 1998 (or so) where you pilot, as well as command, a corvette instead of a fighter. It's got Newtonian space flight, real near space star map and a great story. Even being an old game, it still holds the title Best Intro Cinematic. On the down side, it was fiendishly difficult. I only managed to complete it with the help of an invulnerability cheat (and even with it, some missions were nigh impossible!). I remember the first time I pulled the "drive-by shooting" maneuver, i.e. closing in with the target firing, then flipping over and firing as you face the target but still continue to move away (on your vector) - it was fantastic.
There's a sequel to I-War called "Edge of Chaos", it's good as well, but not as good as the original I-War. It's got more player freedom, but doesn't quite manage to conjure the same atmosphere as the original, IMHO.
Oh, and speaking of space sims, one needs to mention both Freespace games. Good fun, not that much Traveller in them, but good games both. (And to show how old I am, Elite for C-64, of course... plus X-Wing, my first PC game.)
Switching gears here. I just bought Halo (for PC) a few weeks back and, even though I haven't completed it yet, I must say that it's one of the best (if not *the* best) shooters I've played. So far I haven't come across a single dull "scene" yet and being somewhere in the mid parts of the game (near completing the "Assault on the Control Room") with many hours of game time behind me, that's pretty good. Everyone raves about the graphics (and yes, they're great) but the voice acting is also absolutely marvelous in Halo. It's easily the best voice acting I've come across in my 15+ years of computer gaming. The guy who did the Covenant Grunt voices deserves a special mention, I've had to hit Pause a few times as I was laughing so hard it spoiled my aim(!). As I said, I'm only in the middle parts of the game and it's story, but I can say the game really tells a story well - it's the storyline that really pushes the player forward. It is an intriguing and atmospheric story that's well paced. Too bad I know a few spoilers, big spoilers in fact.
So far, my favorite scene has been the beginning of "Silent Cartographer" as the two dropships fly low over the sea. You're looking out of the open passenger/cargo bay of one dropship, as the other zigzags behind. Then both land on a beach full of Covenant troops and drop you with the marines to fight them. A close second, is the first "snow assault" scene, where you first see Covenant "Ghosts" gliders.
While Halo is not 1:1 comparable to Traveller, I've gotten a lot of inspiration from it and a few good story/adventure ideas. The game's a classic, I'd recommend it to everyone (except those who absolutely hate shooters).
About MOO3: It was a major disappointment for me, mind-numbingly boring and "colorless" (atmosphere-wise, no player immersion whatsoever). I wouldn't recommend it to anyone, which is a shame as I really liked MOO2 and had high hopes for MOO3. Sadly MOO3 was a complete miss. If you want a 4X game, go for Galactic Civilations. Even if GAlCiv doesn't look (nor sound) like much, it's lot more solid game than MOO3. The scale is smaller though, so you won't be commanding fleets of hundreds of ships in GalCiv. I haven't Played Space Empires IV much (demo only), but what I've heard is that it shines in muktiplayer and sucks (more or less) on single player. The demo didn't impress me enough to buy it, so I really can't comment SE IV more than this.