Actually, you can get Spanish citizenship in 2 years provided you live in Spain (legally) for 2 years as an Argentine national. You should first become an Argentine citizen, and once you do apply for a
non-lucrative visa in Spain (provided you have enough cash saved up so as to prove you won't work for as long as your visa is valid; once you're there you can work online, though).
After 2 years of residency in Spain, citizens of Latin American countries can apply for Spanish
citizenship. You won't need to take a language test as an Argentine national, but you'll need to take a Spanish culture test. The rest of the paperwork and the process is pretty straightforward. The only problem is the wait; currently around 3 years from the moment you apply, although they are working to reduce that (last year they digitized the entire process and supposedly that will make the wait much shorter).