I can smell a wee bit of bias when reading many articles concerning this matchup. GSP has pleased and attracted myriad of fans, so this is not difficult to understand. Here are the facts.
GSP is in great shape, has a top-notch training camp, and is riding high from fan and media attention, though to say that this is unwarranted would be foolish.
Also, it wouldn't be wrongheaded to conclude that GSP will have significant support from the fans, and that the venue's atmosphere will be in his favor. After all, this is a North American champion up against a South American contender.
Who we support reveals much concerning our own identities. Subconsciously, most of us are likely to support one who is familiar to ourselves and not "the other", or the "unknown."
Otherness is concept that goes well beyond this fight and MMA, but it is an interesting cultural phenomena which also applies to sports.
Back to the match, GSP is a superior wrestler than most, if not all fighters in the UFC, though it would be interesting to see if Thiago's take down defense might render it less effective than previously.
His stand up has improved considerably, but it is Alves who has the advantage in this case. Both men are equally powerful, though Alves is the bigger man. Both train with highly regarded jiu-jitsu artists.
GSP has a five-fight win streak since losing to Matt Serra, while Thiago has a seven-fight win streak, both against top opponents in the welterweight division. In my humble opinion, Alves could have a better opportunity to exploit GSP's ability to take a solid punch or knee to the face.
This is purely speculative, but GSP's chin might be suspect, and with proper power and placement, the two p's, this possible flaw could be exploited by a prolific striker.
I reckon this will be a more evenly-matched encounter than the media and other bloggers will make you think. I hope fight analysis by MMA's prominent media take steps to be slightly more careful and sophisticated in their arguments, so to spare fans from tremendous shock in case of an upset.