The best I have found so far are the Flylow Chemical pants. They are on the slightly shorter side of things (compared to SB specific pants) and they have been really durable so far. Earlier pants that I have used are Analog, Neff and Burton AK. The Analog (well built) and Neff (utter crap) pants were all too long in the legs for my size waist (and I am pretty tall) so the cuffs get all sliced up. The Burton AK (Cyclic) were decent pants but like most other pants don't hold up well to carving. The back pockets were a problem where after a couple of heel-side wipe-outs and the storm flap tore open. Now that back pocket zipper just auto opens all the time. The material also doesn't like dragging in the snow much so the knees started looking pretty ragged after a few years.
I got the Flylow pants at the start of this season and I'm really happy with them, with one caveat: they are the most breezy pants that I have had. While waterproofness is good, they have a ton of vents so a hard wind will find its way inside. This is fine for me since I normally run pretty hot when riding and I guess you can just layer up if you need to. The knees and cuffs have heavy cordura-like reinforcements which seem to scuff up just a little when the snow gets in the way of the knees, but it is holding up really well. The length is absolutely perfect. Long enough that you don't look like a gaper, short enough that you don't walk on your cuffs. They are a bit pricey if you get the current year's models, but I've been able to buy 1-2 year old items direct from Fly Low's website at big discounts.
I've also got a Flylow jacket that I've been using for the past 6 years and despite being made of relatively thin material, it has been holding up really well to lots of abuse.