Personally, I enjoyed Star, but IMO it paled next to the Judy Garland version. Gaga surpassed my expectations, and gave an excellent performance, but I don't think she was better than people who were not even nominated in her category, e.g., Julia Roberts, Tony Collette, Nicole Kidman, off the top of my head, or Judy Garland, for that matter. Did she really give a performance that justified a first-time-out win?
Re Bradley Cooper, he too was excellent, and absolutely deserved his nomination, but IMO not as good in his category as Malek and Ethan Hawke (not even nominated), again off the top of my head.
Both deserved their nominations, but their 'snubs' were no worse than lots of other people who have lost (every year since forever). Let's face it, as much as we love t see people whose performances we loved win awards, the process is totally arbitrary and subjective. Look at Jessica Lange...she gave a GREAT performance as Frances, but the movie happened to open the same year as Meryl Streep in Sophie's Choice, so she was 'snubbed', i.e., didn't win; than she wins an Oscar for an okay performance in a mediocre movie, partially as a consolation prize for Frances, and mostly because she won in a really rotten year for actresses.