How much of a game should be changed when a game company chooses to remake or remaster it?

Blizzard, as we all know, is not averse to doing game remakes or remasters. We’ve seen StarCraft get the treatment, we know Warcraft 3 will get a Reforged remake soon, and we know that Blizzard is very adverse to doing changes to the gameplay itself when they do a remake/remaster. Meanwhile, the Final Fantasy VII remake coming from Square-Enix is going to completely revamp the gameplay, using the system developed for FFXV instead of using the turn-based one from the original FFVII.

I can see benefits and pitfalls to both approaches. Gameplay evolves — keeping the same mechanics and gameplay as a ten- or twenty-year-old game can mean that modern audiences have a seriously hard time getting into the gameplay and end up missing out. On the other hand, doing a complete overhaul of how the game plays or using a completely different style of gameplay risks missing out on the nostalgic among us — and let’s face it, nostalgia is the whole reason for these projects. Doing a remake of a game from so long ago is entirely about pandering to old fogeys like me who want our old school game but prettied up to modern standards.

So that leads us to wonder — which approach is the better one? Should game companies invest time and resources in making the gameplay as up to date and modern as the graphics and sound design and everything else that goes into revamping a classic? Or should they trust that the gameplay is what brought everyone to love the game in the first place and just make it as pretty and flash as possible, trusting that people will acclimate to older gameplay if its presentation is spot on? What do you think is the ultimate goal of remaking a classic?