Although there aren't exactly reboots, Dr Who did change lots over time, different era have very different feels to it.
Now, personally I feel that New Who would be woeful even if it wasn't trying to play around with an established continuity, and that Moffat is trying to preserve RTD's legacy by showing how much worse it could have be.
However, I'm not so much in the majority here.
[small](Oh, and you might want to use the search function, this came up a while ago and there were pages of suggestions, though I don't know how useful they were).[/small]
I might suggest starting with Tom Baker (4), he's very popular and got off to a very strong start, though after a few years his stories sorta went downhill a bit, and Dr Who never really recovered. The beginning of John Pertwee (3) was also very good, but bleak...they weren't sure what direction to take the stories in. When they did, IMHO, they went for a fairly safe, but not brilliant approach, trying to avoid disasters rather than create masterpieces.
Likewise, William Hartnell's (1) early stories are very different to later Dr who, because the writers had no idea what they were doing with the show until a few stories in.