I love your Top 4 (that's three of my own top 3 that year + Sleuth, which I also love). And especially that you love What's up Doc? so much. I couldn't agree more about the chase. I was lying on the floor, when they broke the glass. At this point I'd already recommend you not to miss Paper Moon, which completes Peter Bogdanovich's trifecta of very strong movies early in his career. After that I haven't seen many of his films and I ocasionally like them (maybe we talk about this in 1992 again), but never reached the level of his first three works. Paper Moon is certainly closer to The Last Picture Show than to Doc?, but also has some very fine moments of humour and the chemistry between Dad and daughter is fantastic here.
About 1972 I also can certainly understand your disappointment in Cabaret, which I don't like much either. And I also agree that Last Tango doesn't make too much of it's premise and could have been much more intelligent, but Bertolucci is too interested in provoking people. But for the performances and some good dialogues I still like it.
Now my top films for 1973:
1. The Sting (George Roy Hill)
2. Serpico (Sidney Lumet)
3. The Three Musketeers (Richard Lester)
4. High Plains Drifter (Clint Eastwood)
5. Papillon (Franklin J. Schaffner)
6. La Nuit Americaine (Francois Truffaut)
7. Amarcord (Federico Fellini)
8. Paper Moon (Peter Bogdanovich)
9. Il mio nome e Nessuno (Tonino Valerii)
10. Live and Let Die (Guy Hamilton)
11. The Day of the Jackal (Fred Zinnemann)
12. Pat Garrett and Billy the Kid (Sam Peckinpah)
13. Sleeper (Woody Allen)
14. The Mackintosh Man (John Huston)
15. The Emperor of the North Pole (Robert Aldrich)
16. Les granges brulees (Jean Chapot)
17. The Outfit (John Flynn)
18. Scorpio (Michael Winner)
19. Magnum Force (Ted Post)
20. The Long Goodbye (Robert Altman)
21. Scarecrow (Jerry Schatzberg)
22. Westworld (Michael Crichton)
23. The Exorcist (William Friedkin)
24. Badlands (Terence Malick)
25. American Graffiti (George Lucas)
I'll really leave it at 25 now. I separated it in approximate tiers.
The Sting is my clear #1 that year. Nowadays some people try to diminish it I feel (though I know many as well for whom it's still one of the greatest classics). I think it has one of the wittiest and best screenplays ever, the setting is excellent and Newman/Redford in this film is still my first answer when asked about the best on-screen-chemistry ever.
After that Serpico is a must-see as well, a film that has grown on me soo much at rewatches. It's now in my Top 100 of all time as well. The story of this guy, who just wants to be a policeman and then has to fight his own corrupt organisation is just fascinating and so well directed and acted.
Three Musketeers is a film you will only see in my very own Top 5 probably. But as a lover of the book I still think this hilarious sometimes caricatural adaptation is not only the best - together with it's follow-up in 1974 (and I have seen several ones), but a truly interesting and fitting take.
For High Plains Drifter it depends on how much you like Leone's westerns or Eastwoods Unforgiven. To those films this is pretty similiar in tone. Some scenes are pretty brutal, it's overall a pretty dark movie, but not without humour at the same time.
Truffaut and Fellini made some of their best movies that year, especially La Nuit Americaine, which is about film itsself. Further down on my list you will find (as mostly every year for me) some good thrillers you might want to check out if you like that genre.