I don't have true riding pants yet, but I caught this great thread on SVRider talking about Carhartts Dungaree pants. Sure they're not true riding pants but if you're just settling on jeans then this is an excellent alternative. The canvas duck that they use is so much more abrasion resistant than regular denim. Now, I've not tested these for road rash personally but I've read stories of others that have and they have done well in sub 40mph slides.
They also offer 15oz denim "Loggers" that are much tougher than my Levis. Likely not as abrasion resistant as the canvas but still better than stylish denim.
I have a pair of the canvas in black and the loggers in denim. I love them both. Full cut legs leave room for armor like Bohns or T-Pro. Plenty of room for going over boots. The canvas is quite stiff and will need a wash or two to break-in so to speak. Also, there is a slot in the double-front that gives room to insert some armor. I've not done this but I understand that Joe Rocket shoulder armor works well here.
The black canvas ones look great. My only complaint is that they are a magnet for pet hair. I plan on getting a couple more pairs. These look good enough for business-casual at work so that's what I wear when I ride in to the office.
The denim ones are my favorite jeans ever. Very comfortable and they look great. I will be getting more of these for just general use + riding.
I found mine at the Military Surplus store on Broadway for about $36 a pair, comparable to Internet pricing.
There are rivets on the tops of the double-front. They may touch on your tank as they do mine. So some pliers and about 60 seconds solved that problem.
Here's an article by canyonchasers.net on these pants for riding.
Again - these are not alternatives to true riding pants. But they are an excellent alternative if you're insisting on wearing just jeans and you'd like a comfortable alternative with a little more road-rash protection.