Skyfall is my choice!
I love Javier Bardem as the villain, one of the greatest bond-villains of all time. Similarly Adele performed a top 5 bond theme, really starts the movie with a bang. Casino Royale is great as well. Spectre was good, but it feels too long. They could have trimmed the story a little bit, to make it feel less plodding.
I seriously struggle to get through Quantum. I like the title song. But the action scenes give me a physical headache! There is one action scene every 10 minutes, and all of them use nauseating amount of shaky cam and quick jump cuts. Next time any of you are watching Quantum, pay attention to the action scenes. Every shot last no more than 3 seconds, and then they jump cut to different angle. Add in the shaky cam, and this movie makes me want to puke!