No doubt best combination of reliability, cost, mileage = Honda Civic. You can even get a hybrid. I got one for the wife, its not an accelerating machine by any means, but the gas mileage is great. Going from Vegas to San Diego and back, about 750 miles including tooling around SD, takes about a tank and a half. Tank of gas will run about $35-40 right now at current prices.
A friend of mine has a Navigator and took hers down to SD a few weeks ago, when gas was about $2.85/gallon for premium. She said her gas cost was at least $150.