Every year US-based (but increasingly international) MTB advocacy group IMBA carry out a kind of trail access audit across the US and anywhere else that they're involved in. Scores are awarded based on active local groups, relationships with land managers, access to trails and of course availability of spanky singletrack.
This year's results are now out, and in amongst the usual suspects at the top of the table (Colorado, Utah, Idaho, South Dakota) is Wales. Yes, on IMBA's metrics Wales has the lot - as they say, "Top-notch trailbuilding creates premier mountain bike destination."
The report states: "Wales has some of the best mountain biking in the world, thanks to the whole-hearted support of the U.K.'s largest land management organization, the Forestry Commission, and the efforts of one man, Dafydd Davis. Davis, an employee of Forest Enterprise, had a vision to create a mountain bike trail network unparalleled on the British Isles. Today, the product of that vision is a host of mountain biking centers featuring abundant trails that are very well built"
Scotland, England and Northern Ireland also feature in the report, scoring B+, C+ and C- respectively. IMBA have been accused of being a bit US-centric in the past, perhaps not entirely unfairly - after all, it's only in the last couple of years that they've started to make their presence felt further afield. But these days UK trail builders are teaching the US ones a thing or two - check out the examples of Welsh and Scottish trails on the IMBA site.
And if you want to get involved with IMBA (and you know you should) then trundle over to the IMBA UK site for membership information.