Well that's a snide and ridiculous thing to say. I did say I enjoyed the movie, dude. Perhaps you should THINK about how grownups discuss things with people they disagree with.
I'll give you the respect you denied me and pretend you are in fact, a thinking adult, one that doesn't take a dissenting viewpoint as a personal attack. Perhaps that's a bit of a stretch, I guess we'll see by your response.
SPOILERS
Before I saw the movie I'd agree those were the three acts, but the actual content of them and the non-linear structure belies this, because each section(Past, Present, Future) has a two-part structure, with each part mirroring or matching up with the corresponding parts of the other sections. Therefore the actual structure of the movie is a story told in two acts, crossing over all three eras in each act.
Past = two acts:
-Spain with the Queen(getting the quest, leaving her behind in a futile effort to save her, to her probable demise).
-South America with the Pyramid(reaching the end of the quest, failing, oblivion).
Present = two acts:
-Jackman neglecting Izzy in favor of his research(finding the "cure" = the quest, he neglects her to pursue it, as the Conquistador leaves behind the Queen).
-Jackman regretting neglecting Izzy because she's now dead(she dies, ending the quest as a failure again, he's emotionally destroyed, this is the oblivion).
Future = Two Acts:
-Jackman flying to the sun(the quest).
-Jackman flying into the sun(oblivion).
The third part, being more abstract, necessarily doesn't have the minor variances the others do. Each section has a set up, then the conclusion. No second acts. It's just drawn out because of the non linear format. Just because there's three sections doesn't mean there's three acts.
Since you compared this to 2001, one of my favorite films, I'll use it as an example of how threadbare a plot the Fountain has. Imagine if this were the sequence of events in 2001:
A bunch of proto-humans fight each other. This turns out to be a documentary Dave Bowman is watching on his ship. We cut to the white room with Dave Bowman watching himself as an old man. We cut back to the ship, where Bowman sees HAL go crazy. We cut back to the monkeys fighting. Back on the ship HAL goes crazy some more, explains the star child thing. More white room. Moonwatcher(the proto-human) finds the Monolith, learns how to make tools. Dave Bowman becomes the star child in the white room. Cut back to Dave Bowman turning off HAL. The end.
Now, that might still be an interesting movie(which I thought the Fountain was), but it's not as interesting a plot as what is in the real 2001. The political situation on the moon, the reasons WHY HAL went crazy, the mechanics of how he murders Poole, the dynamics of the proto-human tribes, those are to me part of what makes 2001 a great movie, in addition to the visuals and ultimate theme. Because really, you can have a pretty-looking movie and a great idea, but if the story's barely there or very basic, so what? Because really, that's all that the Fountain ends up being, an interesting premise to hang some cool visuals on. Nothing it brings up is elaborated upon, it's just brought up, then resolved. Every single time. What about the anti-aging thing? It obviously works. How does that affect society? How does the changes in society affect his goal? It's skipped over for a cool visual. Where'd his ship come from? It's just there. We're just to assume since it's the future people can travel to other stars in giant bubbles? Does this have to be addressed for it to be a good movie? No, but I'd like a LITTLE more than just the beginning and end of the story. The middle tends to be the longest part for a reason.
I'm not even saying a movie NEEDS to follow the three act structure. But IMO, this movie didn't pack enough meat to really satisfy me. I found it rather predictable throughout, and for the last hour(it's rather short actually) I kept waiting/hoping for a plot development/complication to occur that wasn't predictable after the first ten minutes of the movie. It never did.
If this movie really blew your mind, gave you a life changing experience, that's great. I'm glad for you. But if you ever bother to read deeper into SF literature, or into the better SF films(particularly some of the Russian ones) then you may begin to see how old hat this movie really is underneath. I'm very glad you like 2001. It's a classic movie. The Fountain however is a very good movie that could be great, and is not, despite how many people claim it is. I do think what IS in the movie is top notch. It's still likely to be in my top 5 for the year. But I don't feel that there is ENOUGH there. At least enough there for me to call it great.
And that's just my opinion.