I, liked many others, started with the 2005 Doctor. In my case it was in 2015. I managed to go from season's 1 thru 8 before I caught up. Then it was one ep at a time. Then being a complete Who-vian, and having an entire year, I went back, watched all of classic. My eyes and mind opened. Now, of course, I have to re watch New I understand so much more and enjoy it even more. For example, first time, Christopher and David were far better than Matt and Peter, and except for River Song, my favorite of all, I thought the story lines were better. What I wrote on IMDB was I now place Matt and David as co-favorites. I believe that having gone back and watched all of classic, gave me a much greater understanding of"the Doctor" and his different faces. The segment of 10, with Rose remains a fave, not so much w/ Martha or Donna, not that I didn't like them, or the shows written with them, but the plot lines with Rose, stood out for me. As did Amy and Rory, their entire run, of course including River Song remains my all time favorite., I also totally liked the "Impossible girl" Clara and how that was written. 11's demise was one of the best of all regenerations. Re Watching the War Doctor episodes also was brilliant! Once again, I could really see where 12 regenerates, they come up with a whoa, my regenerations are used up, I have to re use one, and David re-appears. Well, I still need to re watch Peter, I hope I like him better than the first time around. Well, I strongly suggest that anyone only watching New, go back and watch as much classic as possible. It's really worth it.