Well, I have been flying campaigns for a while since it is not online and it can be relaxing...plus with kids, wife, dog..it is easy to pause and go do what you have to do and come back.
That being said...I am currently flying the "Blue Nosed Bastards of Bodney" and I must say it is a lot of fun.
Tons of detail and the AI is not too uber where you cannot finish the missions. I am currently on mission 9 and I enjoy it alot. One thing though..each mission so far has been about an hour of flying. Start up, take off, cross the channel, fight, fly back land..so be prepared for some time in the seat.
I have also finished the "Rise of the Persian Lion"
This is one AWESOME campaign.
I highly recommend it if you want to learn the F-18 systems better. Each mission seems to incorporate something new so I would review a training film prior to flying and it really helped me in the F-18. Very well made in my opinion and a must have.
On that note..for those Rotorheads (I'm one of them..) The Argo Campaign is phenomenal!! Talk about some flying...whew...again..long missions and landing on the boats is always fun. One mission where you have to rescue guys off a burning sub was kewl! If you want some good missions without being in a server...this is one of them.
The Mi-8MTV2 Oilfield Campaign I have not been flying for a while as there was some glitches in the campaign that have since been fixed, but again...some long missions and some interesting scenarios.