I suppose the best ones would be Louis Philippe, Oasis or Carhartt but any Macy's or J.C. Penney store has some really good ones as well. Amazon has a great selection online that are all rated also.
I've been wearing Gildan t-shirts for a long time and have been super happy with them.
I will go for Adidas
My sister recently gifted me a round neck t-shirt from a brand called Mufti.I really liked the material quality and it is 100% cotton and perfect fit for me.