Criss Angel does a great job at his illusions and they are very believable. I think that they are fake and just tricks, but he goes about them very well and they look fantastic. I think a lot of people like to speculate if he can actually do these things because it is more fun to see more than just a trick.
Yes, he does make his illusions appear to be believable. He is an extremely talented man at doing his illusions, and many people believe that he can actually do the things that he appears to do. He is a great performer, and will never give up his secrets behind his tricks.
Basically, it seems to me that his stunts and illusions take advantage of certain human tendencies, either the blind spots in human perception or by clever misdirection. It's basically the same thing that has been happening in magic shows for generations, only the tricks involved have gotten more technologically advanced and complex as society evolves.
It depends on how you define "believable." Criss Angel's illusions work because it appears that what he says is happening really occurs. Of course, behind the scenes, something else is going on that makes it appear the illusion really did happen. His illusions are believable because we see what happens. Everyone knows there is sleight-of-hand or camera tricks involved in most modern illusionists' arsenals.
Criss Angel's illusions are very believable, but they are, however, pretty cool to watch. Knowing that something isn't actually magic doesn't take away from the fun and excitement of it - most people don't actually believe he really can do magic, but he's a great entertainer that many people like.