Smoked paprika, if you have it. Hungarian (sweet) paprika would be next on my list.
Piment d'Espelette is named for a town on the French side of the Basque frontier. Personally I don't think "paprika" comes anywhere close in flavor---especially the supermarket stuff. I would look for another true pimenton from Spain.
Thanks! That sounds more like what was intended in this French recipe,
Williams Sonoma used to carry a Spanish pimenton that I liked - don't know if they still have it, but that was the easiest place for me to find it.
I agree completely with pierino that piment d'Espelette is in a class by itself. It's even in a class beyond the smoked paprika from Spain. If you don't have it, do what you have to do. But put it on your list of treats for yourself someday. It's expensive, but a little goes a long way.