My 5-year-old loves blue orange games like Zimbbos:
http://www.amazon.com/dp/B0009ICKCO/?tag=absowrit-20
and CooCoo the clown
http://www.amazon.com/dp/B000EPJHO6/?tag=absowrit-20
He's also wild about the stacking robots
http://www.amazon.com/dp/B000ELQVAI/?tag=absowrit-20
Thomas the Tank Engine, Legos, Pixar Cars figures, Play Dough, Dinosaurs are also good bets. He also likes sticker books and watercolor/coloring books and markers (not crayons for some reason -- markers
)
If they've got room for it, a water table or a sandbox is hours and hours of fun.
If you want to get him a video, Leap Frog puts out some catchy ones. If he likes songs the Laurie Berkner has some great music that is very adult friendly (i.e. not annoying like Barney!)
This is a little pricey, but the kids at my son's preschool go gaga over the Mobigo. (It's like a cross between an ipad and a Nintendo DS but for little kids) It's about $90 and the cartridges are around $20, but it's fun for them and the games mostly make learning fun.
For books: Dr. Seuss, Max and Ruby, The Bernstein Bears, Clifford, any of the KUMON workshop books (tracing, coloring, stickers, cut & pasting), Ping the Duck, The Five Chinese Brothers, I Stink, Tikki Tikki Tembo, Stone Soup, Ferdinand the Bull. I could go on and on.
I hope this helps. I'm so sorry for his loss.