If you are looking for a cheap, reliable line you could do a lot worse than Daiwa Sensor. Probably the most popular line out there, a real "Jack of all trades". You could fill up three spools for peanuts and not really have cause to complain.
The "best" line? That's where it gets a little more personal and subjective.
For me? Shimano Technium Black. It has never let me down. Knots well, sinks well, casts well, has very little stretch, and is as tough as old boots. It's more expensive than others, (although some newer brands are catching up), but the best is worth paying for. If money were no object, and I could afford the very best tackle that money could buy, I guarantee that Technium Black would still be on my reels.