price range ? and what games ?
Very important questions.
If your wife plays 3D games... anything that requires DirectX, that limits your choices because it requires you to purchase a Windows machine.
For internet flash games, the operating system doesn't really matter.
I'd recommend a Mac laptop for all casual computer use, IF you're willing to spend the money.
For a CHEAP laptop, or an inexpensive desktop, it's really hard to beat Dell. At the very lowest range of prices, you can have an Ubuntu-Linux loaded laptop for little more than $500-600... or even <$400 for a netbook. However, that's not going to work if you need to play Windows games.
If your wife plays modern 3D games, just throw out the concept of a laptop, and get a desktop instead... get a dual-core Intel @3Ghz(preferably core i7), 4GB (8GB preferable) of RAM, and one of the top Nvidia cards (aim for $250-300 for the video card alone). Make sure to get Vista64 not Vista32... aside from being able to address more than 3GB of RAM, the differences in speed and reliability are significant. Don't listen to Vista naysayers - they either overheard that there were problems and are just repeating it, or they had experiences with pre-SP1 Vista32... which indeed was a pretty atrocious OS. Vista64 SP1 is actually a very usable system, as long as it's well managed.
P.S. If anyone wants to call me a fanboy, know this - I'm typing this post on my work laptop that runs Ubuntu 8.10