Lille - Is it a good city to live?

Depends what you are looking for. (Full disclosure, I'm from Lille)

It's a very young and vibrant city, as students can make up to 40% of its population. As a result there are quite a few concert halls, pubs, so on and so forth giving plenty of occasions to go out.

There's also quite a few places of interests (Opera, museums, zoos etc), historical streets and neighbourhoods.

Most places in Lille proper are well deserved with a fully automated metro, as well as several bus services, easy access to shops and entertainment.

It's really close to Paris (1h by TGV), Brussels and London for these quick 2-days holidays, which is always nice.

If you have more questions feel free to ask and I'll try to answer them to the best of my knowledge.