A Single Man: Fashion designer Tom Ford directorial debut is a book adaptation about a gay British college professor (Colin Firth) who after the death of his partner tries to go through a typical day in Los Angeles. The films technical staff involves many of the artist between the sets and props of AMC's Mad Men.
A Serious Man: The Coen Brothers is the black comedy set in 1967 Minnesota about a Jewish family, primarily Larry Gopnik (Michael Stuhlbarg) a physics professor who's life is falling part and who is having a spiritual crisis of belief.
Common Theme: Both films take place in a similar era, both focusing on professors who feel isolated as they experience loss. Both will likely receive critical praise and awards attention, and both have relatively boring and generic titles.
Not the same: LA vs. Minnesota and gay vs. straight. Not to mention both films will undoubtably have a very strong style judging from reviews and previews, but those styles and artistry have their own flavors.