Co-op shooter w/out split screen is pretty rare, sadly. My wife and I play too and I look for 2p co-op whenever possible.
Most of the non-split ones I've found aren't shooters... stuff like X-Men Legends 1&2, and some sword & sorcery type games. Gauntlet Legends doesn't have great graphics, but does let up to 4 people play at once on the same screen, and it's mostly just running around throwing axes or shooting arrows at monsters. Also has a nostalgia factor for some. :roll:
One problem the single-screen co-op games can have is players getting stuck when the other is on the opposite side of the screen (can happen in Gauntlet). You also can't split up to get different targets. Having first-person POV is impossible w/ 2 players natch, so you may want to consider the split games if FPS is what you're after. It got better when we inherited a bigger TV. :twisted:
Star Wars Battlefront 1&2 rule... [postal]