Best game I've ever played, period.
Ability to play any way you wanted (merc, pirate, merchant, unpaid militia, or even friend of the Kilrathi). If you want, you can change, too.
It has elements of all types of games from action, adventure, sim, RPG, sci-fi, and strategy.
Graphics are superb. Sound creates an atmosphere and adds to the game. Clues are even given by changes in the sound.
Gameplay is balanced, and the entire game can go on without the actual story line ever being touched (although the story does offer some really nice perks).
Upgrades, different planets, trading, and merchant and mercenary guilds. The guilds really add something extra to the game, doling out credits for successful completion.
A little bit of a twist in communications. You can use your communicator to send ship to ship messages in an attempt to change a hostile ship to friendly, or vice versa.
With a linear story line you can stop the story, go get a better ship, and pick right back up where you left off.
Privateer 2. It made a lot of good improvements in the game, but overall just didn't click.
Getting picky, here are some things that could have been better: more ships, more races to encounter, even larger universe, ability to actually make a large difference in the universe, time-line triggered events (like have new weapons be discovered as you progress throughout the game - as it was in P2).
P2 had a lot of improvements, but it totally lost the balance and flow of the game. It was basically just a movie turned into a CD-ROM game.
The Bottom Line
It is NOT another Wing Commander game. Sure, it has some parallels to the WC series, but it's totally different. It's just a well-designed game that actually works! It has a good deal of replay value as you can pick different ships, and you can always try to do something really strange like be a Kilrathi ally. It's really hard to find a game where you can ally with the enemy.