1.) Wing Commander II: Vengeance Of The Kilrathis is not a fun game simply because of the taint of a ship called the Jalkehi. These things frustrate me so much that I get no enjoyment from the game. ... No other ship I've ever seen in a Wing Commander game is so annoyingly hard to face- it seriously just ruins the game for me.
For the life of me, I've never figured out why some people absolutely seem to loathe the Jalkehi. In all honesty, I never found them that difficult at all. A wing of Drakhai Sartha is way more dangerous. Sometimes in missions I'd see a bunch of red dots on my radar, get scared, target one of them, and then think "Whew, only Jalkehi. I was worried there for a minute". In my experience, they were slow, and non-maneuverable, have a huge target profile, fly in a predictable manner, and their rear-gun was way less accurate than a Grikhath's (which, incidentally is faster). You can dance around them, stay out of their front guns, evade their rear turret, and just pound till they die. Yes their armor is kind of thick (although not so much as a Grikath or Gothri), and they do have a reargun, and theorretically powerful front guns (although often they seem to only use their particles), but in my mind they're the equivalent of the WC1 Krants... take time to shoot down and kind of annoying in numbers, but nothing to write home about.
On the other hand, I hated fighting waves of Sartha that gang up on you with their damned neutron guns (like Dralthi II's from SM2), and Grikhaths were nightmares (really effective rear turrets, hard-to-hit target profiles, and pretty fast and well armored, too). But it was Gothri that really took a lot of the fun out of the game (how do I hate thee, let me count the ways, rear gun, fast, thick armor, quick charging shields, maneuverable, powerful forward guns, usually flown by Drakhai).
Maybe it's a function of flying style. I tend to be more like Iceman in style (a dancer who likes to get in, mix it up, and rely on maneuvers to save me) rather than Knight (a steady handed straight flyer) or Angel (a careful gunner that snipes from a distance)--maybe some styles work better against some fighters than others.
2.) The original game aside, all other Wing Commander titles are far easier then this game and the movie ones in particular have difficulty settings so I can enjoy the game rather then play the same mission over and over and end of up having a horrible time rather then, you know- have fun. . .
If you're playing on the higher difficultiles, WC4 is definitely the hardest game. Not only are missiles far more deadly than in any other game (as they should be), but the AI is probably the best combat-sim type AI I have ever encountered. The computer players actually act like humans--working together to put superior numbers to use, pulling off creative and unexpected maneuvers that play up the difference between their ships and mine, etc. I was tailing a Vindicator close to a planet surface once in a Hellcat, and flying a good deal faster than he was, and all of a sudden he hit the brakes and dived for the deck. I was going to fast to duplicate his maneuver and was foced to pull up and fly above him. He then had a perfect view of my tailpipe and ended my day with a HS. I swear, there wa a little guy in my computer flying that fighter, not an AI!
And incidentally, WC is one of the few games where you do not have to fly the same mission over and over. If you fail, then live with the consequence and keep playing. Some of the funnest and most interesting missions are on the losing tracks!