I have been struggling with this lately, my ds was better at playing alone at one and two, now hes four he wants me to play with him so much more. When I say no, he says "I dont love you" "I don't want to be with you, I only love Daddy".
We used to have 5 days a week together, now with nursery and Dad's house we have 3, so by the time we've seen a few friends and been for a few walks and a swim every week that leaves much less down time, he's forgotten how to play alone and I think all of the things he used to play with alone he has tired of.
I've decided he can have half an hour each day during these summer holidays when I will make myself busy, I work from home and usually do my admin in the evenings, so yesterday I told him I need to do some work, and took my lap top upstairs for half an hour, all was quiet and I thought he must be playing nicely, I planned to go down and join him without him asking me to if he did well. So after a quiet half an hour I came downstairs to see what he was playing with, to find him asleep on the sofa, he must have actually bored himself to sleep. Today was much more successful, after a huffy puffy protest sitting next to me I went upstairs again and he went to he's old bedroom to re discover some of he's old toys, I've decided while he is at he's dads this week I will squirrel away a few of he's toys he has forgotten about into tote bags to give him when I wan't to have some space do my work.
My friends children of the same age and younger love playing in their bedrooms for hours.