A lot of them are like bejeweled... you have to align like-items to have them drop off. We play Bookworm and Bookworm adventures the most... that and Windows Solitaire which works very well on a touchscreen.
Today, I installed an Xbox 360 controller and installed all the NES, GBA, SMS, GEN, T16, N64, A2600, & LYNX games and began playing those. But it is primarily a touchscreen system.