Ditto; buy the state parks card for $60 and go to any state park, historical site, or natural area for free (for everyone in your vehicle). I think that's a steal. Even with the entrance fees, I think our state parks are a bargain - just shop some private parks and see for yourself.
As for Colorado: I doubt you've stayed in a "resort" for less than $16. Or Reno. However, if you have, I'd say those were a bargain too!
I'll put the Texas State Park system up against any state's parks. Personally, I think they're too cheap - as evidenced by the difficulty in getting a reservation.