I've played Civ5 quite a lot, and I was wondering if there's a time where it's worth it to use a Great Person for tile improvements on Iron or Salt (for example) ?
Usually I use Great Scientist for Academy, and put it on plains/desert/toundra. For Toundra/desert, I find it very worth it, and once in a while I discover Oil or something under it. I've got to use the ressource, but I never know if it's a waste, or not.
The reason great person improvements collect strategic resources is because those resources are hidden until the correct tech is researched. Putting an Academy on a tile then being forced to demolish it after discovering it's the only source of oil in the region would be immensely frustrating.
As for whether it's worth it, it's not ideal. Usually you're better off building the improvement somewhere else and the appropriate improvement on the resource- especially for later game strategic resources.
The exception to this is if you urgently need the resource. The great person will make it available instantly while a worker will take several turns.
Note that this only works with strategic resources and does not work with luxuries. Building a great improvement on a luxury resource is just a waste of a luxury.
Great People's tiles DO link any resources to your network, so you're not missing out on anything.
Whether or not its a good idea to do so at any given moment depends on a LOT of factors. But putting them down on strategic resources is generally a good idea IMO. Great People's improvements are generally better than a regular improvement (depending on what you need of course).
