Wow, jumping straight to wondering if he's going to be a hoarder--? Please don't put adult issues onto a child who's just doing something totally normal for his age (and for some older ages too). He wants them for comfort and fun.
You've made it even more fun by playing a game with him, though you don't know you're doing it. When you have him put them all away, you're playing his game. Then once you're gone -- he gets to play his part of the game, which is rounding up all his friends again (and again, 2-4 times per sleeptime). He knows by now that you or dad is going to come back and play by having him remove them. You're giving it way too much attention, which is exactly why he's returning all the toys to the bed when you have him remove them. Then you come in that second or third or fourth time and he removes them again, knowing he'll get the fun of having you come in and say "They have to go" and he'll get to play all over again....Even if you think you're being firm or stern about it, believe me, he's thinking of it as a game. Unless he's putting hard or harmful things in bed or covering his face with something soft, he's fine. I'd stop the game and leave it.
Why is it so important to stop it? Because he's playing with the toys and not going right to sleep? Try what one poster suggested and maybe try to make one or two toys his special sleeptime toys. But some kids never do adopt one favorite "lovie" and no adult can choose a lovie for a child; they have to form their own attachment.
Also, he may be on the verge of giving up naps. Many kids do that between two and three. This may be his way of telling you that he's done with naps, and at bedtime, well, it's his favorite game again.
We can't force another human being to sleep, eat or use the toilet when and how we want, and if he's stopping napping all you can do is have a quiet time each day when he's in his room entertaining himself and learning to be alone happily. Sounds like he's well on the way to doing that with his toys -- which is a good thing. You say you hear him, in his room, playing with his toys, and I assume he's not calling for you or crying for you. That's the definition of a good quiet time.