Albert is a highly intellectual man, pushing the barriers of genius level. The man knows how to manipulate both the biological make-up of things, as well as people themselves. He is very good at getting people to trust him, and he is even better at turning the tables away from him to direct attention elsewhere. His smooth and calculating personality make for a deadly man. And he would really have it no other way.
By the time the end of his story comes to a close, it is obvious that Wesker is a little bit desperate. In quick flashes we receive near the end of his time, his temper and more volatile nature do tend to bleed through the icy exterior. He practically gives in the towel by the end of Resident Evil 5, showing that he really has nothing left to lose. Thus, he becomes more and more violent. Which is not to say that Wesker is not a violent man by nature, but when his head is more clear and that rage is more controlled, he is a very precise killer, instead of being wild and rampant while boasting about his ability to change the world for the better.
While Wesker does have the personality of a serial killer, he does seem to have a better grip on reality, at least in everything pre-RE5. He does have a strong knack of planning things far in advance, to the point that almost every given scenario seems to be planned out and exacted. He studies people, understands how they work through infiltration, then turns on them and takes the proverbial goods he can grab. For the most part, he is not a man interested in money or hype - he is a man that is interested in furthering himself, his research, and the the expansion of the human race into something better. It could be that by the time RE5 does roll about, revelations about him could have finally brought him to some sort of breaking point. But that does not seem entirely the case.