I feel like they could have come up with 20 matches that were both most memorable, AND best, rather than one or the other, or one much more so than the other.
Vinci and Williams had a terrific third set, but the whole match was built around a pretty obvious choke job.
Isner and Mahut is one of the most boring things I've ever sat through in my life. After some point each man becomes so tired that holding serve 60 times in a row is not particularly impressive, nor is hitting aces when the returner can barely move.
Soderling-Nadal is historic, and memorable, but it was essentially a beat down.
Why is Pennetta and Vinci any more memorable than say Cilic and Nishikori? It was a terrible match in which both women spent the first set trying to blow it more than their opponent, and I say that as someone head over heels in love with Flavia, and who has massive respect for what Vinci accomplished on semi final day.
Razzano vs. Williams?? It had a great atmosphere, and I enjoyed watching it more than anyone, but Serena has spent the 4 years since then burying it deep. She also has plenty of early round losses at slams, just because this is the single actual first round exit doesn't really mean that much more to me.
Schiavone vs. Stosur? What? Try Schiavone-Kuznetsova at 2015's edition.
Beyond those...
1. Nadal d. Federer, 2008 Wimbledon - I know it's very hip to hate it here now, but it is the crowning glory of a brief beautiful window in tennis history. Watching Nadal finally wrestle control from Federer in those first two sets at SW19 after the heartbreak of the previous years, and then watching Federer refuse to go away quietly and come fighting all the way back, levelling things up with that magnificent 4th set breaker, and then the long 5th. And more than anything else the darkness, and the camera flashes. There will never be another like it. This match and Sampras and Rafter at Wimbledon in 2000 have such an epic quality added to them by the environment.
5. Nadal d. Federer, 2006 Rome
7. Nadal d. Verdasco, 2009 Australian Open
8. Djokovic d. Wawrinka, 2013 Australian Open - Great stuff. As was their follow up at the US Open, and their rematch here the next year. Shame about the 2015 one

What the HELL happened there?
9. Williams d. Dementieva, 2009 Wimbledon - Outstanding, and still hurts every time I think about it
11.Federer d. Roddick, 2009 Wimbledon - It was like David and Goliath. Watching Roddick take it, and take it, and take it to Federer, trying to make it third time lucky, trying to cap his miracle out of nowhere run here off by clambering over his great foe, being aggressive and frankly controlling the majority of the match, but watching Roger in Sampras like fashion just serving like a robot until his all too human opponent finally has given all he has to give, and blinks first. Not
great tennis, but godly drama.
12.Djokovic d. Nadal, 2012 Australian Open - I don't LOVE the match, but it was a hell of a spectacle.
14.Djokovic d. Federer, 2011 U.S. Open - The ending has made it memorable, everything else is why it's best. Two guys bringing the best out of each other. Leagues ahead of their effort from the year before.
15.Sharapova d. Halep, 2014 French Open - Hadn't been a really good womens final at Roland Garros since 2001. This was a great end to a great womens singles.
16.Federer d. Djokovic, 2011 French Open - A real combination of memorable, and best. Great stuff, even without a 5th set.
18.Federer d. Del Potro, 2012 Olympics - Practically any of the matches these two played from this match onwards could have made this list. What a duo.
^These are the undeniables.
4. Nadal d. Federer, 2009 Australian Open
6. Federer d. Nadal, 2007 Wimbledon
^Both ultimately disappointments to me where 4 sets of wonderfulness are capped off by a 5th set of failing.
The Williams and Henin one I don't even remember.
How did they not put the 2013 Mens Wimbledon final on here? or the epic Roland Garros semi that year? How about Tsonga and Nadal in Australia? Or just about any of Baghdatis' matches from Australia in 2006? Rosol and Nadal? Federer defeating Soderling in Paris? How about the double A and Ben Becker at the USO in 2006?

Kim Clijsters winning the 2009 US Open? The semi final if not the final itself!