I’ve always liked
Isabel and
Isabelle.
Isabel has an unpretending charm, and
Isabelle is more dressed-up and elegant but still not too frilly. I’m not too keen on the nauseatingly popular
Isabella, though.
I don’t care for
Isobel. It looks like a typo.
I like
Annabel as well, but it feels a bit on the frillier/more princess-y side, so I prefer
Isabel.
I don’t really think
Isabella and
Bella have ruined the others. I do hate
Izzy, though, and I largely prefer Belle/Bel.