Donkey Kong absolutely deserves a spot in that conversation — the way it introduced platforming fundamentals (ladders, barrels, timing-based jumps) basically laid the groundwork for the entire genre. For me it's a tougher call between the classics, but games that combine tight mechanics with genuine emotional storytelling tend to stick with me longer, which is why Undertale still comes up whenever I think about all-time favorites — its choice-driven combat and writing hit differently on repeat playthroughs.