I'm no longer actively caching, but when I was I did look at other cache listing sites from time to time. I felt, though, that as they had so few listings compared to GC.com it would be rather unrewarding to list on them. I realize that's a bit of a vicious circle - don't list on them and they won't grow - but I wanted my own caches to be found and be found often.
When GC archived all locationless caches I moved my one LC to Terracaching, and the figures speak volumes. In three years on GC it got 203 found logs. In the three and a half years it's been on TC it's had just seven. Obviously it's not a physical cache, but I think the figures still illustrate the difference between sites.
I'm no fan of monopolies, and I'd like to see other listing sites providing healthy competition to GC, but I'm afraid I can't see that happening.
Do not go gentle into that good night.
Rage, rage against the dying of the light. (Dylan Thomas)