Ten different Who fans would probably give you ten different answers, but I'd say check out something of each Doctor and see what strikes you as worth investigating further. The classic series stories move much more slowly than current TV, so there is that to bear in mind if older TV bothers you. Tom Baker's first three or four seasons are my personal favorites of all Who, but each Doctor has something worth checking out. If the Dr Who Magazine all time story ratings pre-Matt Smith are online, pick out the highest ranked stuff for each Doctor (assuming it exists) and go from there.
This, just checkout a few select episodes from each Doctors run and see what you like, if you want to know more than you can go from there.
Off the top of my head best I can think of for each Doctor would be
Willaim Hartnell: The Dalek Invasion of Earth
Patrick Troughton: Tomb of the Cybermen
John Pertwee: Terror of the Autons
Tom Baker: Genesis of the Daleks
Peter Davidson: The Caves of Androzani (I've not seen this myself, but everyone seems to rave about it, I've watched Resurrection of the Daleks way too many times myself)
Colin Baker: Attack of the Cybermen
Sylvester McCoy: The Greatest Show in the Galaxy (personal bias on this one, also Happiness Partol just for him talking someone with a gun pointed at him into killing themself, Seventh be hardcore)
As for McGann, the Movie is OK, but honestly just check out some of his Big Finish Audio plays and listen to them while you're out for a walk or something. Start with Storm Warning or Chimes of Midnight and you'll be hooked.
so which of the following is true:
A. The BBC has no leads on other missing episodes.
B. BBC has solid leads on missing episodes, but can't announce as they're not back with the BBC yet.
C. BBC has other missing episodes in it's possession and is working on restoring for release.
The optimist in me wants C. to be real, I mean they must have had these episodes for a while due to the restoring process (honestly no idea how long that takes) so its within the realms of possibility they have others that they are working on but just wanted to announce these ones now for some reason.
Heck as long as its any of them barring A I'll be happy.