My first was David Tennant, because I started watching the series in 2008. I haven't watched the old DW episodes, only saw the film. The best companion was Donna WITH A MILE. I loved her humour!! and Alex Kingston as River Song is really good indeed. I'm biased, I just loved everything that is Doctor Who.

(and on the old ETS the thread's name was Dr. Who, and it was so bad. I hate when people write it this way)