It's all about the design, the xbox 360 has such a bad design... First of all, Microsoft puts the hard drive on the top and fans to the side. Well that adds a lot of pressure, think about it; the heat will go upwards (going to the hard drive) a good way to think about this is a balloon. When a balloon is released into the air, it moves upwards so does the heat. My recommendation is that you get internal fans because it must be your graphics cards that is spoiled. The xbox 360 has good graphics but the graphic's card cannot stand the heat... Since the xbox 360 almost uses all of its power (when playing), it creates a lot of heat but gets stuck into the small fans. After hours of wonderful gaming, your console freezes.
I would recommend cleaning the console for possible dust accumulation, or else check the ventilation ports/buy a fan to avoid/prevent. If this doesn't work, sue Microsoft!!
I don't think that the xbox 360 is a bad console but just a regular Microsoft product. You can always expect all types of errors in Microsoft's products (from slow-freezing Vista PC's: RROD xbox 360: not working Windows Defender: Unsecured OS). But if your asking which system is better, the Playstation really is a heck of a system, though the xbox 360 has a lot of games it is just quantity but not quality.
Yes the PS3 is a more reliable system, if not look at crashing rates, for instance; 6 out of 10 people who had xbox 360 was deffective (this was at the very beginning of the release), and now it has reduced to somewhat 32% (All consoles since 2005), yet more and more cases have been reported. Also the fact that Microsoft hides this fact... makes me wonder.... As for the Playstation 3, have no idea... So I wonder... Are there any problems for the PS3? Well one thing I'm sure of, is that PS3 has not had as bad system failures as the 360 has.