The reason I personally like BST north of the Divide is because it is a fairly easy uphill with good sight in all directions and just enough technical riding to keep advanced riders entertained without being overwhelming to newer riders.
I like BST north of Ogden Canyon because there is less traffic and as you get further toward the Nature Center it gets quite rocky and technical. Most people will have difficulty past the intersection for Jump Off Canyon's trailhead. I only know of a couple of people that can ride the rocky, technical section out AND back. I think more riders will be able to do it as they try it on a fat bike, but on your typical mountain bike, you WILL get worked. This is part of the appeal to me. It's always challenging and I consistently have to walk less of it.
I think the biggest thing OBP has going for it is all of the trails are one way only. That means that you can open it up and really rail the perfectly formed berms. You can also see most of the park from the top of the trails so you have a pretty good idea if someone is on the trail already or if someone is looking to come up despite the one-way only signs.
Skyline trail to Ben Lomond's saddle is another personal favorite. It's another one that takes far longer to get up than it does to get back down. It has everything you could want in a ride; step downs, rocky sections, rooty off-camber sections, fast flow, and amazing views. When you ride it at night you can see all along the Wasatch Front, down into Ogden Valley, and up into Cache Valley. You can see mountain goats, moose, and deer on many of the rides up there. Plus the dirt and ecosystem change as you get further up. I can't relay how much I love this trail. Skyline is one of those trails that is physically demanding, but everything in life seems better after you've ridden it. It's one that you have to experience yourself.
I think the routes most worth mentioning are the East Fork/Middle Fork loop, Sardine Peak Loop, and Ice Box Canyon. East Fork/Middle Fork is a fast flowing route that you can hit Ice Box Canyon on the way back down. Ice Box is steep, technical and beautiful. Sardine Peak ranks up there with BST as far as a favorite among locals, but because it's been the route for Xterra Nationals for a few years, it's on many rider's lists of must rides. I personally prefer to ride Sardine counter-clockwise, but because I made the mistake of trying to ride it that direction on a Saturday morning, I learned that most people like to ride it clockwise. Sardine is wide open for most of the ride because you have good visibility, but there are still some switchbacks and blind corners, and because it's a popular trail also, expect someone to be around that blind corner.
Let me know if you think there is anywhere I forgot to mention that you love to ride.