I've been using Morgan Blue Syn Lube for years on my bikes. It's thick and gloopy and it turns black within a few yards but works very well, particularly in wet weather (although I rarely ride in the rain). I recently decided to try a different lube and went for Muc-Off C3 Dry Ceramic lube. I noticed the difference immediately across all of my bikes. It doesn't attract too much dirt and the drivetrain feels a little smoother during pedalling and shifting. What I find really good about the Muc-Off C3 Ceramic is that it's really easy to apply, only needs to be applied to the inside surface of the chain links, and it contains a UV marker which lights up with the supplied UV flashlight so you can see exactly where it's been applied. Downside: it's really only for riding in dry weather and it's very runny so some drops will fall onto the floor.

Of course, everyone has their own favourite chain lubes, but I'm just going by real-world 'feel' which is the most important criterion for me.