To me the best ski pant is one with no insulation at all. That way I can add layers beneath it, from super-light to moderately heavy, and handle any temps from mid-30s down to zero or colder. I can even change things around mid-day if need be. Insulated pants just don't offer that flexibility.
A good example of this? The Burton Cargo Pant ($150). They're made from a waterproof-breathable laminate; have a clean, uncluttered design; and can be layered over anything from silk or merino wool long underwear to bulkier fleece. Patagonia's Snowshot Pants ($160) have very similar specs but with a slightly less "urban" look. You even can wear the Snowshots without an extra layer, since the inner face of the fabric is soft, brushed polyester.
Bibs also are great. They offer more warmth and moisture protection. Marmot's Randonee Bib Shell Pants ($350) are made from Gore-Tex Pro Shell for great breathability, waterproofness, and durability. Pricey, but really great pants.
I usually pack three choices for a base layer. In mild conditions, Patagonia's Capilene 1 Silkweight Bottoms ($45) are ideal. For an all-purpose base layer, try either Icebreaker's Bodyfit 200 Legging ($70), made from merino wool, or REI's Midweight Polartec Power Dry Long Underwear ($33). If it is really cold, Campmor's Polartec 200 Trail Blaze Pants ($45) can go over either of the other two bottoms, and under the hard shell.