Ajay Devgn goes first in the ranking and below will be my opinion on each actor.
Ajay Devgn >> Akshay Kumar >> Aamir Khan >> Hrithik Roshan >> SRK >> Salman Khan >> Ranveer Singh >> Varun Dhawan >> Ranbir Kapoor >> Tiger Shroff.
Ajay Devgn: He's very versatile and part of the reason why I'm a fan of him. He may not be at good comedy but not the worst. However, he's very underrated in romance e.g. Pyaar To Hona Hi Tha, Hum Dil De Chuke Sanam, Dilwale, De De Pyaar De and etc. His biggest strength is intense roles in action masala movies and even offbeat films. Plus, he's excelled in emotional scenes very well e.g. Dilwale, Zakhm, Apaharan, Hum Dil De Chuke Sanam and etc. This is why he enjoys balancing different genres because it's called versatility.
Akshay Kumar: Akshay has done a wide range of genres like Ajay Devgn even today both actors trying out different type of movies. He's excelled in action movies superbly and has made a career out of comedy which audiences have loved him in. Romance he can do his own style and emotional scenes he's good enough to pull it off.
Aamir Khan: Aamir is a perfectionist no matter what roles he does. His chocolaty boy hero image which he has proven that he was good in romance. Comedy is superb and knows how to get the timing right which not many can do. Emotional drama is Aamir at his best e.g. Dangal, Rang De Bastani, Fanaa, Ghajini and so and so. Lots of unusual roles he has done makes one versatile actor. However, he needs to try more things out like Akshay & Ajay do.
Hrithik Roshan: Another versatile actor who has done unusual roles but has proven that he do action movies. I mean his stunts in Dhoom 2, Bang Bang & WAR shows that he's Tom Cruise of Indian Cinema. He's nailed it emotion drama e.g. Agneepath, Fiza, Mission Kashmir, Koi Mil Gaya and etc. Plus, intense roles Jodhaa Akbar and Agneepath in such powerful performances. As I mentioned with Aamir, he needs try more stuff like Ajay & Akki in terms of different genres.
SRK: SRK can portray different kinds of roles if it comes with heart and soul. I mean the risk he gave in Baazigar & Darr shows how superb his hence emotional drama scenes. When it comes to romance, nobody does it better than him because he has the innocence and body language to pull it off. I mean he's played obsessive Darr and normal lover in DDLJ. Action masala movies, he's good but he needs to explore more in this genre hence an action film should be his comeback.
Salman Khan: No doubt he's master when it comes to masala movies in which audience want to see him in. He's not bad emotional drama e.g. Tere Naam but comedy and romance he done a good job. Loved him in Andaz Apna Apna, Judwaa, Biwi No.1, Jab Pyaar Kisise Hota Hai and ect.
Ranveer Singh: He's overrated and not the best actor but not great. He was good in Padmaavat, Bajirao Masanti, Gunday and ect. Overreacting in many roles even Simmba in some parts of the film. He's not capable of pulling roles like Khans, Ajay, Akki & Hrithik can do nor he can't act in them.
Varun Dhawan: Varun needs to have his own style rather than copying Govinda and Salman Khan which is why he looks fake in comedy. Plus, he overreacts as well although he gave a good performance Badlapur. & ABCD 2 He can do better if creates his own identity.
Ranbir Kapoor: I don't want to say anything about romance & comedy because I find him annoying these two elements. Action movies is something he can't do and I don't think audience can imagine him in macho type character. However, he's good in emotional drama and I liked him in Sanju which is his best performance.
Tiger Shroff: There's a reason why I have ranked the lower simply because he's bland in terms of face expressions and dialogue delivery. He's fantastic in action scenes but even in this genre, his performances are very poor. That's why is hard to digest him as an actor but it seems that he doesn't care and has no desire to improve his action. He will do action movies as long as his stardom is there.