I never did get to play the PC lucas space sim games...have always wanted to but at the time I didn't have a flight stick and my PC couldn't handle it...so I'd have to go with Freespace just due to the fact that I have actually played those games
Darklight Conflict was an awesome looking game, and I loved the gameplay...but it wasn't close to being a "Best of the genre" type of deal. I particularly loved the manual docking you had to do after every mission. The game, as I previously said, was one of the last advanced DOS games before gaming moved onto Windows...and IIRC it was entirely software based rendering as well. The PC version had great controls and the PSX version (that I later purchased) was not the best port IIRC (controls took a hit and visuals had a low framerate, worse textures, game lost the almost voxel-like quality of the visuals and was cluttered with tons of low polygon models with obvious seams...if memory serves correctly). To be honest, I don't remember the music...so I'm unsure if the music in those videos was added by the person who posted them or if those western tunes are actually from the game.
When I was playing this game, I was also playing through Wing Commander Prophecy...which was another awesome space flight game...and I was basically in space sim bliss...nearly a week after I finished Wing Commander Prophecy, Freespace came out...and I was absolutely floored. Later on, I bought Colony Wars and didn't see what any of the fuss was about. So...meh...
edit: Outside of Factor 5's first GC game (Rogue Leader?), I haven't enjoyed any of their flight games...they all have a same-y feel to them...I'd hope they stay out of the Space Flight genre, personally.