There are lots of great board games for 5 year old boys. Boys this age love playing games with parents and families in particular as well as with their own friends. In the article below there are lots of educational games by Orchard toys as well as some classic board games. 

Orchard Toys do a great selection of games for young children which are very educational and great fun too. The games below are aimed at kids aged 5 and up.
The Magic Cauldron game is a fun game which helps teach some maths principals without children realising they're learning. 
Pop to the shops is a good game to teach about money.

5 year old boys are old enough to start playing some of the classic board games that have stood the test of time. Snakes and Ladders is good for counting up to 100 and fun to go up the ladders and down the snakes.
The Charades for Kids is great fun for all the family. Younger children have fun looking at the pictures and acting subjects such as lions, dogs or cats in the alloted time. Older children act out subjects like eating spaghetti or doing up shoe laces. 
Hungry Hippos and Connect 4 is a great classic game that kids can play with other children or with adults.