What were the greatest chess tnmts ("Top 10") ever before and after 1950? You can interpret greatest as meaning the strongest or most famous, your call.

My list, prior to 1950:

1.  London 1851

2.  Hastings 1895

3.  St Petersburg 1895

4.  San Sebastian 1911

5.  St Petersburg 1914

6.  NY 1924

7.  NY 1927

8.  Nottingham 1936

9.  AVRO 1938

10. The Hague 1948

Baden Baden 1925 was pretty strong.

After 1950... Hastings 1963/64, won by Mikhail Tal would be my pick.

Maybe Vienna 1882 and London 1883 would belong up there somewhere.

At Chessmetrics these are ranked as the eight strongest tournaments ever, and the only events to have all the seven strongest players of the time as participants:

1. Vienna 1882 (Steinitz/Winawer)

2. Linares 1993 (Kasparov)

3. Nottingham 1936 (Capablanca/Botvinnik)

4. AVRO 1938 (Keres)

5. Linares 1992 (Kasparov)

6. Wijk 2001 (Kasparov)

7. London 1883 (Zukertort)

8. Wijk 1999 (Kasparov)

Wow, looks like Kasparov is highly rated at Chessmetrics!

On a list of the strongest tnmts ever Vienna 1882 would definitely have to replace one my picks prior to 1950, possibly London 1851 which would still qualify - on a list of the most famous tnmts prior to 1950.

It's interesting to note that Kasparov won 4 of the 8 strongest tnmts ever!

Bad Nauheim-Stuttgart-Garmish 1937. Four players: Euwe, Bogolyubov, Alekhine, Saemisch.

Yes, and still Las Palmas 1996 isn't ranked up there by Chessmetrics, maybe there are reasons to count that as one of the strongest tournaments ever even if it only had six participants and can't compete with the "everyone in the top seven"-events.

The field in Las Palmas 1996: Kasparov, Karpov, Anand, Kramnik, Topalov and Ivanchuk. Kasparov and Anand had played a title match the year before, when Ivanchuk won Linares. Topalov won five strong tournaments in 1996 and reached 2750, while Kramnik shared first with Kasparov on the rating list after several great results and Karpov was just five points behind after beating Kamsky convincingly in the FIDE title match.

Kasparov won the tournament with 6.5/10, Anand finished in second place with 5.5.

Tournaments where most of the top ten players of the time were playing:

Before 1950: Baden-Baden 1870, Vienna 1882, Hastings 1895, Carlsbad 1911, San Sebastian 1911, Moscow 1925, Bad Kissingen 1928, Carlsbad 1929, Nottingham 1936, Avro 1938

After 1950: Zurich Candidates 1953, Reggio Emilia 1991-2, Linares 1991, Linares 1992, Linares 1993, Linares 1994, Linares 1998, Linares 1999, Wijk Aan Zee 1999, Wijk Aan Zee 2001

Yeah, but if you look at some of their older players' ratings and then look at the games, it's pretty clear they are overcompensating somewhere. 

The last several years - at least three - the Tal Memorial has had most of them, too.

I think it was 2010 when all the Top 10 except Topalov, who was #2 at the time, wasn't playing.  Some chess journalist asked Morozevich if they missed having Topalov so the entire top ten were in it.

Moro replied, "Topalov is never missed."