no, you'd use the past because Bob is no longer alive: the nicest person I've ever met was Bob - Bob was the nicest person I've ever met.

Bob may be dead and he was a nice person while he was alive, but the meeting people in your life is still on-going.

Thanks, dude. The answers in the back of his workbook all had "is". But the student had to fill in the answers himself. (Practicing superlatives)

My first impression was that you would say 'The nicest person I've ever met is Bob Smith' with the full last name, if the name is the news item, answering the question 'Who's the nicest person you've ever met?' With only the first name, the name is evidently not the news item, so it might be better the other way around: 'Bob is the nicest person I've ever met,' answering the question 'What do you think of Bob?' or 'What's Bob like?'

In AE we would often also say 'Bob was the nicest person I ever met' if there's no likelihood that you will meet him again -- definitely if he's dead, but perhaps also if he's just moved far away or you've lost touch with him.

Whether that matches the BE textbook rules, I couldn't say.

To take an example with different words:

Jack Kennedy is/was the most handsome president the US (has) ever had

I (BE) would use a past in the main clause (because he's dead, or perhaps even because he's no longer president) and a present perfect in the relative clause because the US still has presidents. The tense of the verb in the relative clause seems to be to be unstable (I can imagine a past tense), but I would find it positively weird to say 'is' in the main clause.