Though it's not my all-time favourite, I'd say Castlevania is the most sentimental for me. I had it back in the day, and it was game my original NES wing-man loved most. He was one of those guys who liked to watch you play while he'd help out in other ways, like with mapping or directing you from magazine tips as you played. Anyway, our life ambition, as far as gaming was concerned, was to beat Castlevania, though we never could. Time past, and eventually we learned that his family was going to move far far away. So what did we do with our last ever day together as little 12 year old friends? Castlevania, that's what! We spent over THREE HOURS at Dracula, but still couldn't beat him (yes, we were pretty shitty players back then, I guess) and we failed in our quest.
Yada yada yada... he walked out of my life and I drifted on to SNES then N64. But when I finally got back into NES again, and before I even considered myself a collector, I hunted Dracula down and drove a stake through that slimy bastard's heart. And now all is right with the world... the end.
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My mantra, as worded by SamSpade on 06/12/12:
I don't resell to fund my collection, I don't treat this hobby like a second job, I don't care if my collection is worth ten bucks or ten thousand because I never plan on selling it. Seriously, what does the value have to do with anything if you never plan on selling? Speculation doesn't mean jack shit to me at this point, I just want to play my nes games...