Samsung makes every part of the system, firstly. They manufacture the flash memory, DRAM, and controllers. They are typically first to market with new process nodes for making memory products, so their density/cost ratio is pretty good. Having that vertical integration lets them keep their prices relatively low.
So I can pick up a TLC NAND flash SSD for about the same cost as the competition and expect it to be nearly as fast as older, more expensive, MLC products. Same for QLC, competitive with a lot of similarly priced TLC models from the competition.
As for being the best, that comes down to a cost/performance and durability. There are faster drives out there, but they usually come out after Samsung's products.
Intel Optane, for example, can't be beat for latency figures, but is still significantly more expensive.