Strike Commander was the only flight sim I really enjoyed.

Enemy Engaged : CvH for reasons mentioned above, is definitely one of my favorite flight sims. The strategic layer that wraps around the individual missions that you fly makes the dynamically-generated missions more meaningful.

I don't really play the hardcore race sims because I don't have a racing wheel. I do know that SimBin published the free Volvo: The Game which might be a good way to assess how much you like driving sims.

I liked the tank sims Panzer Elite and T-72: Balkans on Fire but I've only spent a bit of time on both of them.

The problem with vehicle sims (aircraft, spacecraft, land vehicles or even Mechs) is the time spent learning how to operate (and/or fight in) each vehicle and extracting maximum performance from them takes a lot of time, which probably explains their niche status.

Also, I would actually consider managerial games to be another category of sims in a certain sense (feel free to disagree) e.g SimCity or the sim-lites like Tropico (which I highly recommend)

Propilot - never did learn to fly properly and the manual was enormously thick (as in, goodish sized paperback novel) but dang, if it wasn't awesome when I could get off the ground.

Oh, and Traffic Giant was pretty fantastic too, does that count?

Well-known, not-yet-mentioned, super-awesome-sleep-depriving sims:

Rollercoaster Tycoon franchise
The Sims franchise

Since sims are mainly about vehicles, how about my favourite vehicle managing sim - OpenTTD. The original Transport Tycoon Deluxe that OpenTTD is based on, is also pretty awesome.

I would say that depends on the simulator and how wide a net one casts with simulators. For instance, one could make an argument almost all games are simulators depending on the definitions one uses. :)

I like combat flight sims quite a lot (maybe you can tell): IL-2 and Red Baron happen to be my favorites. I've got one of the Enemy Engaged series but haven't had the chance to try it yet.

To me and this goes back to the definitions one uses, I'm not sure if space sims should really count as true simulators since they aren't (by and large) simulating something that actually exists. But, be that as it may, I like the Freespace & X-wing series; I like what I've played of Independence War; and I will probably pick up the Wing Commander series when they go on X-mas sale.

City management sims can be fun too (Sim City and Caesar III).

However, for your amusement, there is this:

http://www.gamespot.com/street-cleaning-simulator/videos/the-gamespot-community-reacts-to-street-cleaning-simulator-6328075

I have to try that Street Cleaning Simulator! and all the simulators for vehicles that I can't drive in RL.

As downloadmunkey says, some "study" simulators are pretty detailed and take a bit of time and effort to master. Microprose's Falcon 4.0 (with the BMS mod) as well as F-15 and F/A-18 from Jane's are my favourites in the fighter/fast jet category. They also include options for easier gameplay.

If you're more into historic aviation (i.e. WWII era), IL-2 is perhaps among the best.

If you want a more simplified look into the world of modern fighters (through the software-rendered goggles of mid-90s technology), Jane's Fighters Anthology should definitely be considered. I don't think there exists a PC game which is more rich in flyable planes, world objects, missions etc. A true classic which really should be made available through GOG.

Lock-On: Modern Air Combat is perhaps one of the best-looking "survey" sims.

Sounds like you're an experienced Falcon 4.0 pilot :) Any chance that you've tried FreeFalcon 5.5? it looks pretty neat but I only have access to a netbook right now and it refuses to run on that (understandably)

Wet - The Sexy Empire
Game Tycoon
Biiing!
Mad TV

All of them old and really good :)

Well thank-you sir, I shall look into each of these, especially Jane's Fighters. You seem to be pretty high on that game. I've definitely heard the name IL-2 before, perhaps seen it during a Steam sale. It goes on special pretty often, should I check that out as well?

yeah, that's it. Rub it in, will you -_-

Perhaps you've seen IL-2 on GOG? I haven't picked it up since I only have a gamepad and not all sims work well with them - self-centering axises and that fuddly stuff. Joysticks are pretty much the de-facto controller for any serious sim.

A decent sim-worthy joystick can be quite cheap these days.

There's also this series of games, but the prices are far from introductory and the developer still hasn't made a single demo. https://store.thirdwire.com/store.htm
I think, I ended up getting all of them only due to post-release "early adopter" discounts.