I have two approaches in mind, really, because I don't know the intention of your question (i.e. finding the best denomination for yourself, or fact-finding for some kind of research project).
The only resource I can point at for a reliable baseline on teaching/doctrine is the Bible. "By this all will know that you are my disciples - if you have love among yourselves". This is how Jesus pointed out what identifies his true followers in John 13:35. That implies there are also un-true followers, warned against in Matthew 7:13-23. Unity in teaching and thinking is also referred to as important aspect of true discipleship (1 Corinthians 1:10, 1 Timothy 2:8, 2 Timothy 2:23,24). Because I learned to look at the Bible for answers, I'm not really involving myself in all the beliefs that vary in interpretation, because that might be a lifetime spent - or wasted. As far as I am concerned, there is only one biblical truth that takes personal time and effort (study) to find.
As far as my understanding of different denominations goes, the numbers I heard have varied to as much as thousands. On this page you find some list, but first glance already tells me it's somewhat outdated. It does, however, provide links to potentially useful resources, such as Wikipedia.
Significant to consider is the statement that more than 2 new denominations are formed each day. In addition to that, beliefs within professed denominations such as, say, Catholicism, can vary greatly. Then, is number of registrations a reliable figure in this case, if a large part does not even share the beliefs associated with the denomination? Relating to the previous approach, the question is asked wether or not all the denominations can actually be classed as Christian. According to the Bible as referred to above, they cannot.