As far as remakes go they're not horrible (despite buttmad toys for bob employees trying to get people to hate them as much as Crash 8)
There's some aesthetic downgrades since the devs are actively fighting current engine tech to make them.
I'd mostly recommend skipping relics in Crash 1 and 2 since they weren't designed for them.
Mostly I'd recommend not buying them since you're giving Activision, and, by extension, Microsoft money.