Well, people who say there are the best either a) Do not have a good ear. b) Are of the fanboi variety. c) Haven't actually listened to a decent system.
As to why the prices are high, Bose has one of the world's best marketing department and have convinced people in a and c that they are better than they actually are and converting some of them into b.
That's not to say that some of there speakers don't sound decent, there are far far worse stuff out there. However, they don't really belong in high end discussions. The goal of audio systems (when were talking home audio given the context of your question) is to play back the original performance as accurately as possible. Bose' speakers tend to be rather colored meaning that they overemphasize certain frequency ranges and underutilized others. They just cannot be accurate to the recording. There's other issues too, imaging, soundstage presence, etc, but it's easy enough to stop at coloration.
As for what is best, I'm sure there's an implied price range in there hard to give a good answer without knowing what it is.
I have owned a Bose Cimemate system. When it died I took it apart and was amazed that the Bass unit only had a Paper/Foam 4.5" driver which is pathetic for a Bass driver. Yes, it was ported but you would still have a hard time getting any Bass from such a unit. Sorry to say Bose makes people think they are getting good quality when in fact its all smoke and mirrors. The main speakers are the same with paper composite material. Its no wonder they lack Treble. The only people who buy Bose is wealthier people who want simple setups and know very little about good quality sound.
I bought my Cinemate system at a Bose outlet and only for TV sound. I would never buy anything Bose if quality and accurate are required. Bose does a good job creating equalized sound through electronics because it is a cheaper way then actually buying quality speakers and using good amplifiers. In other words, they hide the fact that they use bad speakers. It is one reason that Bose never advertises their specifications. Their are some independent tests that have been done on their Cube systems and their results show a very inaccurate and poorly designed product. At least from the standpoint of equal frequency response from 20Hz to 20Khz. Their is a very good reason why Bose seals up their systems so you cannot see the bad quality of speakers and why their systems are only demo straited apart from other systems. They do not want you comparing a really accurate system with their artificial system. My advice is stay away from Bose unless you find their artificially controlled sound to your liking. Just remember it is not accurate sound.
Bose engineers better housings and EQ for average quality components. However, listen to your ears. If you can't tell the difference between Bose and Browers and Wilkins, then it doesn't really matter does it?
while it may be true that bose uses standard grade components, inadequate speakers, and shadey marketing this does not mean that they are not a good choice for idividuals who have no desire to look into options other than a HTiB solution. i've heard bose next to all of the typical speaker systems and it holds its own with them.
however, any decent speaker system will always sound much better than "HTiB" sets. the quality level is normally quite significant. the downside is that prices are higher and there needs to be at least a bit of research or knowledge in order to get the right products.
can you exceed bose quality sound and stay under the bose high price? well sure. the average person doesn't want to do the research required though so they stick with what they see in front of their face. its up to the individual to decide.
as for me i'll stick with my own system. for only a few hundred more than the larger bose system available i put together a pioneer vsx-30, klipsh quintet 5.0 & klipsch 450w sub. a little more setup work but well worth it.