Who's the Hero in LOTR?

I was at a house warming party once. (I know this seems completely off-topic. Just stay with me, okay?) I met a bunch of new people, and one of them was a young man. He was a writer (not full time - just as a major hobby) and so he told me a lot about his stories and I told him some things about mine. Then we got to talking about the inspiration we got for story writing. I said I got inspiration from reading really good books, like Lord of the Rings. Instantly, I realized I hit upon a gold mine there. We talked for ages about it. But the first thing he said was,

 "So, who is the hero in Lord of the Rings?"

I wavered, a bit confused. "Well... I... I'd never really thought about it properly before," I stammered.

He waited, patiently. For a long while, I awkwardly tried to think really hard, but nothing clear came to mind. 

"Well, it could be a number of people," I mumbled, "I guess Frodo is generally considered the main character." I looked at his eyes and knew I had to give up. So I asked him, "Who do you think is the main character?"

"Sam."

WHAM. That was a new idea. I'd always considered Sam as the loyal friend, the secondary character, always beside, supporting his Frodo. He was the sidekick - the "add-on" to the 'main characters'.

And it made me realize how much I underestimated those quiet, loyal characters that don't ask for fame or stand out in the spotlight, and yet they're some of the most vital to the story. In a way, it helps me see how important people who are like that in day-to-day life are.

Everyone knows that person who hardly says a word, but is always there to listen for you; who never searches to be the centre of attention, and yet everyone thinks well of them. That person who doesn't come to mind when you think of a hero, but who, when you consider it, rescues the story. 

So it really hit me hard, that Sam was one of these. He didn't seem like the main character - when you first meet him, you certainly don't think he'll play an incredibly vital part to the story. But, as the young man pointed out, Sam truly was the cause for the Ring ever being destroyed. He was the cause for Frodo ever making it to Mount Doom. Sam really was the hero.

(For the record, though, I don't agree with everything that young man said. (He tried to convince me that Peter Jackson should have added the part when Saruman tries to take over Hobbiton, but I stubbornly stood my ground. I think the story ended perfectly well without that part and I always felt it seemed a bit 'out of place'. His argument was that it showed the strong, courageous side to Hobbiton which probably would not have come out otherwise. Before that, Hobbits were just known for eating and gardening etc. However, I'm still not convinced. But that's a discussion for another time.))

What do you think?? Is Sam the hero of Lord of the Rings?