Here's what I saw in the first fight:
1. Canelo fans were gonna see Canelo winning every close round (Adelaide Byrd, ahem)
2. GGG fans were gonna see GGG blow out Canelo and win 9-3 or 10-2
3. Canelo won 2/3 opening rounds, but GGG had a really good case for the first round (even though he didn't get it on the cards)
4. GGG cleaned house for the next 6 rounds (4-9). Canelo really didn't do much of anything but react (ironically, here, the Canelo fans that gave Canelo the edge for winning close rounds against Lara for aggressive criteria, in some cases, were the same fans that gave Canelo the benefit of the doubt for fighting in the opposite manner).
5. GGG stopped jabbing in the last 3 rounds and Canelo used that as an opportunity to come back into the fight. The last three rounds had arguments for both fighters.
6. GGG was actually out-boxing Canelo from the outside. It was during the exchanges where the fight got close.
GGG gets one of the first three and one of the last three, and with the middle six, he gets an 8-4 decision.
You really had to give Canelo the benefit of the doubt for the first 3 and the last three to even make it a draw.
Here's what I think about the rematch:
1. Canelo knows he can take GGG's power.
2. GGG is used to the build up and atmosphere (something he was not used to previously).
3. Canelo is a bit sharper in the pronlonged trades and gets the benefit of every close round even if it is a coin toss - unfair, but he throws loud combos, even if some are wasteful and do nothing.
4. GGG's eyes got used to Canelo's speed (not a problem for Canelo since GGG has never been a fast fighter), which sounds insignificant, but explains why it took GGG a while to adjust in the early rounds.
Overall, I'd say that Golovkin has the room for improvement. If he makes a couple changes, he can win. Namely, he is best keeping Canelo moving back and jabbing him. He needs to put the right hand or body blows behind his jab. There really aren't that many changes that Canelo can make. He pretty much did the best he could. Canelo will be the same. Still though, there is a story about leopard's being unable to change their spots, and another about teaching an old dog new tricks that works against GGG. GGG's age (he has slowed over the past 2 years, PM if you want a significant elaboration), and his willingness to get carried away and trade will work against him no matter what.
So the rematch becomes very interesting. It'd be nice to see the sequel in New York instead of Vegas. Put it in MSG since GGG is the 3x champ, Canelo is not.