Do a search on this topic. There is no correct answer to this. It's subjective and completely dependent on a bunch of factors specific to a particular use.
Your other posts make you out to be an expert of sorts in these database systems so don't you already have an opinion? "best" is so subjective anyway... what criteria are you judging it on? stability? scalability? cost? or are you thinking of your own employment prospects - how quickly you can become an expert, what you can earn?
MYSQL is free and you can use for small projects. Oracle is not free but is the best. You can use PostgreSQL is free, the syntax is close to the oracle.
MySQL is available on most sites without doing anything to have it available. Oracle has to be installed and, unless you own the computer the site runs on (or the one Oracle will be running on), you might not have that choice.
MySQL is easy to use and available for everyone to use free. Oracle is not free and also require proper techniques to develop it. But if you can successfully handle Oracle then it is the best option.
MySQL is good for light database, But if you need a large database then Oracle is best than any database as it has very advance function and keyword than any database language.