I played rFactor 2 for a couple of years and raced GTEs and GT3s in the Virtual Endurance Championship and GT3 Endurance Series.
I really enjoyed the team aspect of the races and built some great friendships that have lasted even now I've taken an extended break from sim racing. The highlight every year was the 24 Hours of Le Mans - I have really fond memories of doing the night shift at 4am with the one or two other people online, knowing we had to carry the car to the morning.
I really enjoyed the multi-class racing. There was always someone in my mirrors and the first couple of times the prototypes would come to lap us each race would always be so hectic. I can vividly remember the feeling of dread being in a very intense battle at Spa, having the leaders stream past us leading up to Eau Rouge.
Another thing I loved was just racing as part of a team and the pressure of not letting me teammates down. In a weird way I enjoyed the underlying feeling of dread in the couple of days leading up to each race, the peaking in the laps before I took over the car, and then in longer races, the way the fact it didn't go away after my stint as I knew I had to get in the car again later on! Then when we'd cross the line, there was always such great relief knowing that I wouldn't have to get in again.