7. The longest era
Another obvious reason why Tom Baker is remembered so well today is frankly how long his era lasted. While many Doctors usually last for 3 seasons, Tom Baker played the Doctor for 7 full seasons. Decades later, the only Doctor that came remotely close to matching that was his predecessor Jon Pertwee - and his era only lasted for 5 seasons. Still a more than respectable number, but still 2 shy of Baker's record.
It really is incredible to think about, especially for a Doctor's era. Honestly, it's shockingly rare for any UK show to last as long as 7 seasons. In fact, when I think of shows lasting that long, I tend to think of US series, such as Star Trek: The Next Generation or Elementary. (My wife introduced me to that show, and honestly, it's a surprisingly solid take on Sherlock Holmes.)
For one single Doctor to have lasted so long in the role is incredible. And honestly, the only reason it wasn't longer was because Tom Baker suggested leaving. If he hadn't, it's a very real possibility that he could have lasted even longer.
There's a part of me that's glad he didn't though. One of my favorite elements of Doctor Who is the fact that it changes so much, and always brings something fresh for a new generation of viewers. When Baker left, Peter Davison enjoyed a solid run of his own as the Fifth Doctor.
But that doesn't stop how long Tom Baker lasted in the show from being an incredible achievement. More than that - he was the Doctor for countless children and adults for a long time.