Series 5 probably will get the title of best ever but I would agree with Bluey - 6 is my pick. I just love the constant tension and danger with them being without their mothership and instead stuck in "the Bug." The sci-fi element of RD is at its peak and while it is true that is equally mindblowing in series 5, the gags per minute style in Doug's final co-written with Rob Grant series - the Lennon and McCartney of screenwriting for me - puts it just about ahead. Series 3 I adore and that is my 3rd favourite series - the first 3 are some of the best RD episodes ever and marked a new phenomenal era (though series 2 was incredible too) and the 2nd half is extremely close behind and I even love The Last Day. Series 2 to 6 are the peak of the show to me, series 1 very good (the comedy was first rate but the plots were "just getting going"), series 7/8 half successful/half bungled evolutions to me while BtE is the weakest - though still okay - IMHO. Series 10 was RD pretty much back on track while series 11 and 12 without scaling the absolute heights that 2-6 reached, were excellent (9 out of 10) and the finest RD in decades. But anyway if series 5 wins I will be delighted but to me it is just by a slight margin the 1993 run that is my favourite.