Eh… pardon moi, but Gypsy Kings are supposed to have influenced who? Not a lot of people in Spain, for sure, as there they’re seen as a one hit wonder and that one hit was a discoified version of a lolailo classic. Other groups did flamenco pop and flamenco rock before them, with much longer-lasting success (los Chungitos for example, and their sisters Azucar Moreno, just to name two which come to the mind of this absolutely-not-lolailo poster). Then again, Gypsy Kings are French.
Spanish music has lots of different people, separated by gender. After all, ok, yeah, Elvis is huge, but so are Prince or Duke Ellington - in different genders (of music, sillies, not of underpants!).
The bestestest metal guitarrist from Spain is Rosendo (Mercado), or at least he’s the one who is more likely to get you yelled at if you dare say within a metalhead’s hearing that he sucks; as well as solo and guest work, he was head axe for Leño (other classical metal bands include Obus and Barón Rojo - Barón’s Metalmorfosis was one of my favourite records for years, and I was no metalhead). The bestestest guitarrist in general is Paco de Lucia, who is most famous for classical work but has done about any gender you care to name.
The most influential punk band is probably Siniestro Total. I’ve seen them classified under other labels (“ska” and “world music” among others… uhm…), but “punk” is what they started under.
Alaska, in all her incarnations, has run the gamut of music on the edge. Punk, electronic, whatever.
Loquillo (“too rocker for the punkis, too punki for the rockers”) is instantly recognizable, as is unclassificable Joaquin Sabina.
I refuse to name that guy that foreigners think is good and who lives in Mayami, Flohrida. Light pop of the fluffiest kind, and the interpretative ability of a dead snail on a rotten wood plank. If you like his ehr, songs, argh, may I recommend you Argentinian Maria Dolores Pradera? The same song that Mayami man can use to put a marmot to sleep will, in La Dama’s voice, make a statue break out in tears.
And of course, Manolo Escobar was bringing lolailo to parts foreign way before Gypsy Kings or Las Ketchup, while Lola Flores is and will always remain La Faraona… the queen of flamenco. Just don’t tell anybody, but like many non-lolailos I prefer Doña Concha Piquer.
Celtas Cortos, heavily influenced by the french Gwendal and the Irish Chieftains, have been the foremost (ok, the only one with large success) Celtic group for years. If you like your Celtic more metalized, get some Mago de Oz.
Most famous pop group, probably Hombres G, although Mecano is close up and Radio Futura can’t complain about their sales.
Peret can be credited with inventing Rumba Catalana, whose current flagship is Estopa.
Serrat and Miguel Bosé are in the list of influences of pretty much any Spanish artist who isn’t on some totally weird branch of music. Oh, Serrat’s full name is Juan Manuel or Joan Manuel, depending on the year the record got printed… just search for Serrat 
Note that with the exception of Estopa, everybody I mention either has been around for a long time or isn’t any more. That’s a bit of a requirement for the “influential” part, usually.
lolailo: flamencohead