Novak, Murray and Soderling all performed better at the majors in 2010 compared to 2009. Not to mention, in 2009 Nadal was absent for a couple months and when he got back his form wasn't anywhere near what it was at the beginning of the season.
You're focusing on specific player's performances while I'm mostly looking at slams (which are tourneys that entertain me the most, always did) and my opinion on level of play.
In 2009 we had:
-2 top echelon players in great form at AO, Fed and Nadal (the level of play off the ground in their match was sick).
-At 2009 FO while Fed was a nervous wreck in Haas match (understandably given that Nadal got upset the previous day and it was now or never for Fed) his level of play was pretty high the rest of the tourney (especially in his SF against Delpo), Soderling was playing really well obviously, Delpo was also playing terrific tennis (something people forget, I watched him throughout the tourney and this is the 1st time I thought that this guy might be a slam winner soon) and it was the last slam in which Gonzo played at a very high level.
-2009 Wimbledon, Fed and Roddick were on fire, Roddick's aces per match in that tourney were Goran like (and on slower grass) and his transition to the net was never as smooth as it was in that tourney, before or since, finally he approached well and used his serve to great effect (even against Fed).
-2009 USO, Fed and Delpo were in great form.
That's for slams, those aside, there were great Nadal-Novak CC battles in every CC masters, Novak played terrific in 2009 Paris masters and Kolja was in the form of his life in 2009 YEC/WTF.
Fed's level wasn't great in 2010 after AO either, but at least he was there, he wasn't absent for 2 months.
It wasn't great is putting it lightly, it was mostly horrid for his standards, especially his Wimbledon performance where he played some of his worst grasscourt tennis in his career (he looked better in his 2002 1st round Wimbledon loss to Ancic and 2000 1st round Wimbledon loss to Kafelnikov than he did against Falla).
Also, you are leaving out 2008 as one of the toughest? 2008 was WAY tougher than 2009 & 2010 and it was also tougher than 2012 by not by a big margin.
2008 is up there.
2008 AO - Novak was playing some of his best tennis, Tsonga was in the zone and Fed played good but not as good as he did the next year IMO.
2008 FO - Best career performance from Nadal on clay and probably the single most dominant slam performance I've ever seen.
2008 Wimbledon - Enough said, epic tourney even though I didn't like the outcome.
2008 USO - this is where the level wasn't on par, Fed won mostly through solid play and say what you will about many of the 1st time slam finalists in this era but they all showed more fight than Murray did in that final.
Still, despite that USO performance this was a breakthrough year for Murray, won Cinci, reached USO final and then won Madrid after so that's a plus.
As for the "way past his prime Ljubicic" comment, Ivan himself said he played the best tennis of his life at IW2010. It's not like he got to #3 like he did in 2006 though...
What else is he gonna say after his biggest win? Sampras said he played his best ever in 2002 after he won USO, Novak claimed that 2012 he played as good as he did in 2011, Agassi was claiming he played his best tennis in his 30s etc.
I don't take anyone's statement/opinion as a given, I form my own opinion and no while Ljubicic was playing very good tennis and did well to take advantage of the opportunity when it presented itself his overall level of play was much higher in 2005 and 2006, I followed the guy almost his entire career and there's no doubt about that for me.