A good web host is one that offers reliable hosting with superior support and whatever other features you need for your particular situation. And, of course, most of us webmasters want this also at the lowest price possible.
The only obvious first distinction between the good and the not so good web hosting plans is the bandwidth they allow you to use. The more bandwidth, the more visitors your web site can have. Any web hosting plans with less than 5Gbit of bandwidth allowance per month (or with unlimited bandwidth) are simply not worthy of your considerations.
Most hosting providers now a days offer very similar web hosting packages at very different prices. And while some of the very cheap web hosting providers, under about US$5, have to cut corners to provide you web hosting at that price - which will reduce their service and reliability - many of the more expensive web hosting companies don't necessarily provide better support or service.