I'm going to cheat n my very first answer, because I'd choose not a single painting, but the entire Chauvet cave system with all of it's beautiful art, contours and delicate crystal tracery for me to be able to contemplate at leisure. The single sweeping line of the lion (the first, and best single line painting ever done), the panel of the horses, the oxen drinking from the well - I love them all!
But back to the real world ....... for me it would have to be Rousseau's painting 'Suprised' (I've spoken of my love of it before). I have a high grade framed copy of it already, but anyone who has seen the light shining forth from the impressionist masterpiece's in Paris will understand the difference between even the best prints and the original paintings. Suprised is a naive work of consumate skill (and Rousseau was untrained) that quite simply throws activity at you in a single flash of exposed intent. I can drop my eyes on the painting and rest them there for as long as it takes.
Now, what's your choice? Take your pick, whatever you want!
