Topic of the Day:
Big time Francophile here, so.... Seurat, Monet, Manet, Caillebotte, Delacroix, etc., etc., etc...
As for favorite paintings... It really is truly amazing how seeing a painting in person is such a totally different experience from seeing it reprinted in a book. Even though paintings are essentially a two-dimensional art, there is definitely a third and fourth dimension added to them in person. The brush strokes, the texture of the canvas, the layers of the paint, the reflection of light... I was particularly struck by the first Rembrandt I had even seen in person. On paper, they look like portraits, but "in person"... So much more. Much more. (Ah, a Fantasticks reference.
But my favorite painting for a myriad of reasons is Seurat's "...La Grand Jatte". I still remember crying the first time I saw it at the AIC. Beautiful.