“Lost” is back, better than ever, and just what this strike-ravaged TV season needs. Some observers criticized ABC for deciding to air the eight completed episodes instead of waiting for the full batch of 16 scheduled for Season Four. But judging from Thursday’s action-packed, emotional opener, fans of the show will be delighted with an abbreviated run. The new season continues the mind-blowing Season Three finale, adding new conflict and deeper mysteries. So who are the Oceanic Six? What secret do Jack and Hurley share? Can’t wait for next week.