If your budgets is <$1000, the costco systems are the best deal that I've found. The 4 channel systems are only about $300 when they go on sale. I've got 3 of their 16 channel systems and have been satisfied with them. The quality is OK at best, but you can compensate somewhat by better placement/more cameras. In the sub-1K range most all the systems are about the same. Biggest problem you'll have is probably the night vision. No matter what they claim on the specs, most of them suck at night. You might be able to make out a person, but reading plates and identifying faces is going to be tough past about 10 feet.
If you want to step up to better quality megapixel IP cameras, it's going to cost you at least 3x-5x more money just for the cameras alone. That doesn't include IR illuminators/software/NVR, etc. I've priced it out, to get a comparable system to what I have (16 channel, 8 camera), but in an IP system would run about $7K, and that's only about half of them megapixel cameras.