My 8 yo daughter loves to pretend play with me; we play my little ponies, we dressed the ponies up make up stories etc. I give her half an hour of pretend play and then she goes on to play by herself, but I always do the effort because she really likes playing with me.
since she was an only for 7 years, I've been her playmate all of her life, my most fond memories of her is when we played together. we build cities with legos, chase each other, played polly pockets, dress up pageants, made experiments. now that she will be 9 she has besome more reserved and I miss those times, but still she will want me to sit and play with her.
I know it seems boring or silly but after you start playing you get the hang of it and he will be so happy. just tell him, ok buddy you have half an hour (or an hour) to kick this Jedi's butt, lol!
have fun and enjoy these times!