Barneysmeg Well i wont argue with you, that Rose is one of the best, but when she left, she wasn't replaced, martha and donna are companions in their own way, he has a different relationship with each of his companions, i don't think you can compare them too much, other than the fact that they are all loyal, trusting, beautiful, quick witted, everything a companion should be. After Rose, the doctor was a bit fragile and so didn't see the signs of marthas unrequited love for him. And Donna was the best mate, who had no feelings for the doctor and it was just proper friendship. Rose was the love of his life. So really they didn't take her place, because that what happens the doctor moves on from one to the next and each one is different and unique in their own way.

SpikeVamp  Rose is the best I'm not gonna lie shes my favorite female character in any show or movie ever except for Buffy from Buffy the vampire slayer but that's a different story. But i really liked Donna because was just so funny and she was just the doctors bbf and stuff. And i hated Martha because she was just because she was annoying and boring but not because she replaced rose because she wasn't really posing a threat to steal the doctor's heart from rose or anything.