1. Jean Grey (O5) - Her solo made me love her and it probably helps that I've only read X-Men: Blue and not All-New X-Men
2. Wolverine (movie version)
3. Cable/Iceman
Cable & Deadpool gave me a healthy respect for Cable and I've loved Iceman's recent solo.
Honorable mentions: Rogue (movie version), Gambit, Cyclops, Havok, Angel (O5), X-23