As already pointed out by Siddarthan Sarumathi Pandian their is no best language, its all about which language you are comfortable with.
But, Using Express (Node) over other languages will give you advantage of processing the same code over server if you want to server render some of your functionality (For SEO, Fast first load).
So, if you are learning and no specific preference of any language go with Express (Node) for a React applications and you will realize certain benefits it has specially for JavaScript (Angular, React) based applications.
For DB, you can go as per your requirement. If the application has high volume of transactions and less reads ( Range of millions ) RDBMS databases will work fine. If you have high volume of data and reads (+ most data is of same format ) go with noSQL based DB's (MongoDB, CouchDB).