the important thing is to analyze the performance in long term not in short term.
for example with altcoins if you look at short term you sometimes will be fooled by how well they are doing. for example the most random altcoin goes up 90% in one day! but when you look at the bigger picture like a year you can see that small rise was only in a short period of time and never lasted.
interestingly the exact opposite is true with bitcoin. it is as if you took the altcoin chart and reversed it. bitcoin has big drops in short term and they never last. a small dip and then rising all over again.
Yes but in times of touble Bitcoin seems to be doing pretty well. In fact it has fall down only couple procents and qucikly recovered