Comparing it Deadpool and Guardians? It's not really inferior to either in all honesty. Disclosure, I've seen all three and currently own one of the aforementioned films and I can say that they are all breaths of fresh air in these genres. Guardians was fantastic and Deadpool was just crude and funny to a point where you just grinned at everything. Suicide Squad deserves to be in those same conversations. Suicide Squad was really funny and the audience was laughing quite a bit. I just don't understand half of the criticisms towards SS because it's fine if Disney or Fox do it with Marvel properties, but sure enough, DC has a funny ensemble or somewhat crude film and it's dashed by critics and the moviegoers who hold these critics up on pedestals.
I have one piece of advice: go see Suicide Squad for yourselves and be ready for a good, action packed fun time.
I don't understand why it's so important to put a number scale on something since we all have different personal scales, but if Guardians is an 8/10 for me, Deadpool a 6/10, then Suicide Squad is right in the middle at 7/10 for me. Deadpool had one thing going for it: Reynolds and his quips. Guardians had the cast, humor, and villain going for it. Suicide Squad definitely has the cast and humor as major pluses.