In my opinion, bitcoin is the strongest, but no other coin can beat bitcoin, because the bitcoin users are pretty much so the other coins can not beat the bitcoin.

That is right, with a lot of users bitcoin will be unstoppable and I don't think even if it dumps hard, users will be more aggressive taking it as an advantage of buying a lot of bitcoins and hold it for a long period of time. For now, let's be active and HODL.

Among all the currencies I think bitcoin is the one that's reigning all through out. After everything that has happened during the fork and other events that occurred, bitcoin is still standing firm and probably increasing its value continuously. And when it comes to users of bitcoin, it is very obvious that there are lots of people who uses bitcoin than any other coin.

I think BTC's strength is falling because of new cryptocurrency launched, for example like REcoin.

Well, i think that your best choice should be bitcoins. Because not only it has gone through a lot and survived, but because it is well known. Plus the developers are hands on in maintaining and if not, making bitcoin better and easier to use. We can only expect better things happening to bitcoins from now on.

you can see on some sites a cryptocurrency market capitalizations like coinmarketcap there bitcoin ranked first it shows bitcoin is the strongest compared to other cryptocurrency. safe or not it depends on how you hold it and your strategy especially if there is panic sell.

The better option for you to invest your money for long term is bitcoin only and I don't think that any coin can take place of this coin because it is that coin which have more stability by price and also by technology .
If you will compare bitcoin with another altcoins then you will find that fee coins have the same technology that the bitcoin have but still thier progress and reliability is not good like bitcoin .
So if you want invest your money  thrn go for the bitcoin And if you want make sudden profit then yiu should invest your money in the bitcoin cash , because bitcoin cash is the coin by the same team of the blockchain bitcoin , so it will be morr better for us to out the money in the bitcoin and bitcoin cash ( BCH ) .

There is always risk involved in investing in cryptocurencies but regarding bitcoin I think it is one of the safest as what you say because almost all people involved in cryptocurrency have bitcoins in holding and/or other cryptocurrency which means that they're confident bitcoin will have significant value in the future. It just reached its ATH and from speculations, they think it will have corrections and will have a bull run again after that so accumulate coins as much as you can. The demand of bitcoin is increasing by the day and in fact companies like Starbucks, Subway, Dell and Microsoft are already accepting bitcoin for some of their transactions.

In my own research about bitcoin it becomes the most reliable crypto currency with a very firm fortitude. I blame my self why i did not join bitcoin when it was introduce to me last year. Now we will need a huge amount to buy bitcoin if we need to start investing of bitcoin.