As you can see, starting a "best caliber for deer thread" is about like asking if Ford or Chevy makes a better pickup truck. You're going to get all kinds of different suggestions and opinions and probably end up more confused than when you started. Look at some ballistics charts.
Hornady has a good one on their site. Compare the velocity, energy, and trajectory of the three calibers.
Remember that using the right bullet for the job is even more important than choosing a caliber. That will also open a whole other can of opinionated worms.
To be honest, a case has probably been made by someone for every caliber between a .223 and a .375 h&h being the "best deer caliber ever." There is no such thing as a best caliber because everyone hunts different terrain for different size deer. Everyone is not the same size and therefore the same rifle will not be best for everyone. Everyone has a different level of tolerance to recoil. With all these variables it's a good thing we have all these wonderful commercial calibers to choose from.
Maybe one day one of these best caliber threads will end in total agreement by everyone and we can all hunt with the same caliber. Wouldn't that be nice?