Not sure.
Think there's more than one dimension to it. Fields were definitely deep in 2009 but not super top heavy.
Depends on how many top players you consider. I decided to check for 2009 YE top 9* in QF berths and here it is:
AO: 7 (Simon)
IW: 7 (Ljubicic)
Miami: 7 (Tsonga)
MC: 5 (Wawrinka [SF], Ljubicic, Beck)
Rome: 5 (Gonzalez, Monaco, Zverev)
Madrid: 7 (Ljubicic)
RG: 5 (Gonzalez [SF], Robredo, Monfils)
Wimbledon: 4 (Haas [SF], Hewitt, Ferrero, Karlovic)
Canada: 7 (Tsonga [SF])
Cincy: 4 (all of Big 4 made the semis while all of the QF losers were non-YE top 10 players)
USO: 6 (Gonzalez, Cilic)
Shanghai: 4 (Lopez in SF + 3 QF losers)
Paris: 4 (Monfils [F], Stepanek [SF], Cilic, Tsonga)
*I chose the top 9 because a) #9 Verdasco got to play the YEC since Roddick withdrew; b) #8 Söderling and #9 Verdasco were separated by 110 points while #9 Verdasco and #10 Tsonga were separated by 425 points (and Tsonga only overtook #11 Gonzalez by 5 points so it would be misleading to include one but not the other, and top 11 would be too much I thought).
Solid top9 heaviness on HC, Cincy and Shanghai not so but the former had Big4 in the semis and the latter had Davydenko besting Djokodal consecutively in epic fashion - only Paris was relatively weaker, as usual.
Less so on clay, but the Djokodal trilogy makes up for it, Novak presenting a new and exciting challenge.
That leaves Wimbledon and RG, which are rather remembered for specific matches: RG the SöderKing upset and the five-set semis (plus the Fedsterclass in the final but that's not a plus for competitiveness), Wim for Roddick beating Hewitt and Murygoat in cool battles and then becoming the best GS losing finalist ever (ehehehe). Certainly more memorable than some 'strong era' slems.