(In irregular intervals, I will rank the airports I've visited according to their adequacy for airport hiking. Please remember that some of the requirements for interesting hiking trips, such as a challenging topography, are detrimental to most other functions of an airport. This includes actually catching a flight, which some people still consider to be the primary use of an airport.)
Good: LAX, JFK, CDG, EWR, HI, SCL
Probably good: YYZ, LHR, FRA, PMI, EZE, GRU
Boring: BCN, MUC, TXL, DUB, SXF, AGP
Can't remember: MAD, ATL, STN, LYS, NUE, DTM, VIE
Too small: EDI, GLA, BFS, BHX, LGW, LEI, XRY, HAJ, YHM
Definitely too small: EXT, KLU, LSC, ANF, ZOS, ITO
Forty airports. I didn't quite expect that.