1. Where are you using them? (and no, I don't want you to reply with "on my legs")
i.e If it's for low temps - e.g. high Rockies, then waterproofness (if that's a word) is not as important as e.g. in Andorra, where you might want to sunbathe on the grassy slopes between the rain in a bad season, or in Scotland, where you can get blown up the slopes in driving rain.
2. How much do you want to spend?
I have 2 pairs I use:
1. Phoenix Black Diamond Gortex from about 4 years ago (cost around $200). They're great in the wet.
2. Tenson MPC from last year (cost around $150). Ideal for cold conditions, very windproof, and good waterproof.
I'm not sure if either of these brands are available in the US (they are British and Swedish respectively), but they are excellent. another one to look at is Fusalp (French brand).
I chose Tenson over Fusalp last year because of comfort and fit, which if you're buying ski gear is very important, unless you are a logo skier, in which case I'm sure Tommy H or DKNY have something in the right colour!
BTW Over here many people talk about Gore-tex being the best. There are other similar products on the market that cost less.