On its own, as SD has pointed out, Seven Samurai does hold up very well. However, I feel obliged to talk some about it's director who is perhaps one of the most influential directors of all time.
Akira Kurosawa, like his samurai, was a master of his discipline. He was thoughtful, intelligent and a perfectionist; a recurring sight in Seven Samurai is a revelation or plot point being revealed either next to or involving water in some way which is important to Japanese culture.
The action is limited but the drama leading up to the action is fantastic. Each character feels well-rounded and we are given plenty of time to become empathetic to what they are trying to achieve despite what has gone before between the villagers and samurai. Historically, farmers were wary of samurai as it wouldn't be uncommon for them to either raid their crops or even burn them and leave the farmers in a hopeless situation. This friction is constantly referred to throughout the film and provides an emotional gut-punch when one of the samurai begins ranting about how the others behave towards the farmers.
There is only one choice here for me, and it is for Kurosawa's masterpiece. Plus I feel it is worth noting that both Lucas and Spielberg have said several times that he was a big inspiration to their work, with Lucas even using the blueprint of one of Kurosawa's other films for that whole Star Wars thing.
Seven Samurai.