I just watched the Marquez vs. Pacquiao bout.  I thought it was a pretty great fight.  With that being said, the only time I ever watch boxing is when a big fight happens.  

To answer your question, perhaps your right but MMA historically always had the biggest events happen at year end.  Examples include Shockwave event in Pride.  Liddell vs. Silva last year and Liddell vs. Ortiz the year before.  Jackson vs.  Griffin will be a pretty big fight in my opinion but that is a long way off.  Penn vs. Sherk is big in terms of importance.  Lastly, a possible Fedor vs. Barnett or Couture would be important and large.  

Silva vs. Henderson was a very big and important fight and I thought it delivered since Henderson won the first round before Silva submitted him in the second.  I guess you say it would have been better if Henderson could have survived and gone to decision but that asking alot against Silva.  

Are we talking 2008 or 2007?

No...it's not.

I think a big point is that MMA is putting on a larger number of interesting, entertaining fights that aren't the headliners or for titles.  There have been some great fights in the lead-in matches of UFC PPVs, and some even better fights as dark matches.  That, of course, assumes you're judging by the quality of the fight itself rather than the significance of the fight in the larger scheme.  It's two separate questions, and with respect to the second, yes boxing has had more significant fights so far, but MMA has a number coming up.

Also, if we're talking the sport as a whole and not just the big promotions, I have also been impressed at the improving quality of small MMA promotions, like HCF (based in Alberta).  I can't say whether or not boxing at that level (where "significance" is obviously not a particularly useful criteria) is featuring a high level of skill and providing good entertainment, but the MMA shows I've seen definitely are.

Not that MMA (UFC) doesn't do go overboard with them, but all three of the fights you mentioned are rematches. Something to consider.

Also something to consider are other "landmark" fights, e.g. Mir vs. Lesnar. This fight has nothing to do with the best fighting the best, but it has a lot to do with growing the sport and expanding the fan base, something (ostensibly) some of boxing's mega fights are supposed to do.

As a huge fan of BOTH sports I'd have to say that it depends on how you look at it. I don't think there have been any instant classic MMA bouts this year while boxing has already given us two instant classics in Vazquez/Marquez III as well as Pacquiao/Marquez II.

But with that said, the sheer number of quality undercard bouts we've had from various MMA events this year blows boxing undercards out the water where there has yet to be a single great undercard fight on any of the boxing ppv's to date. I agree that boxing has stepped up it's match making (ie the end of the Top Rank/Golden Boy cold war) due to MMA's surge in popularity, but until they start giving us halfway decent boxing undercards the promoters still have a lot to learn.