The amount of fun one gets from a recycled level lies in how the developer recycled.
The sloppiest form of recycling would be sending you back to a dungeon (or other equivalent area) that you have already explored just to find some random macguffin for no good reason. That is just blatant time-wasting.
On the other hand, if the developer recycled a level by changing even a few key parts of its construction, then you could (theoretically) be granted a new and fun experience. I think the best example of this would be to send you through a city to chase down some random something or other then send you back the way you came through that city only this time the city has been recently nuked into rubble. It's all about creative use of resources.
The sloppiest form of recycling would be sending you back to a dungeon (or other equivalent area) that you have already explored just to find some random macguffin for no good reason. That is just blatant time-wasting.
On the other hand, if the developer recycled a level by changing even a few key parts of its construction, then you could (theoretically) be granted a new and fun experience. I think the best example of this would be to send you through a city to chase down some random something or other then send you back the way you came through that city only this time the city has been recently nuked into rubble. It's all about creative use of resources.