Well, anyone can answer this question because most Indian grew up watching this movies. So I am not going to go into every single cliches. Because there's a lot. Instead I am going to mention some general ones and then most importantly I am going to explain why that is exactly.
Because it is important to point out the flaws but why that is more important.
Cliche number 1>
Looks, Looks, looks. Mr Roshan and Deepika Padukone.
Unless you look like her or him, you should live boringly or don't deserve anything.
Cliche number 2>
Finding love is the ultimate goal when without money and job or business everything else is meaningless in real life
Cliche number 3>
90% movies are love stories. Almost as if there's nothing exist other than love between two characters.
Cliche number 4>
Nerds don't get girls or hunk. So even if you are one, you can adapt. But in real life people change very slowly. Atleast in Indian context
Cliche number 5>
Happy ending. Really!!! Happy endings. In real life happy endings are rare.
These are all basic cliches of Indian movies, I am sure a lot more exist. But the point is not that. The point is why do they exist in the first place?
There's reason why bollywood do what it does
Look, India is still a Conservative society so they can't really show everything like western movies.
There's a lot of taboo attached and yet bollywood producers in their mind need to show something that is attractive and not boring to make viewers to buy tickets to go watch it in hall from Indian stand point as a result one would get certain over glamourised doctored version of reality because conservative society tend to be boring for silver screen
Having success in life is more important than anything else. After all you can't love someone when you are hungry :D
But Indian society is Conservative traditional one, it can't go beyond certain things.
This success in life is so very important and yet Indian society's conservative life style doesn't permit one to be truly professional. Because when a person truly professional, he and she can only then increase his or her true potential to work eithic hence a lot of progress in work place hence a lot of income.
What is truly professional?
Everything in your life centred around your job or business, your relationship only exist to take care of your mental aspect to be more efficient in your work place which means you don't necessarily have to have those traditional Indian marriage system, maybe one night stand and short term relationships are more suitable in that way. Basically relationships are there for you so that you don't feel alone and get distracted in your job or business.
Relationship are not primary in your life
Why am I saying all this?
Because most of the bollywood movies are copied from Hollywood movies. I am talking about rom com ones.
A guy in New York works in some MNC and then he suddenly met a girl in train who works in some NGO.
They talked, they laughed, they spent one evening, they made love to each other, they moved on to their lives next day.
Suddenly, hero and heroines realised that they are missing each other.
Love story starts.
This is a common plot in Hollywood rom com.
Bollywood copies it and make Indian version movie out of that.
But underlined line they are missing that unlike Indian society, these people's lives are not centred around marriage or family rather their job.
In the meantime, they sleep with their opposite gender not to feel alone.
They are potraying a perfect life of true professional which does not happen in India.
Because we don't know the meaning of true professional which is why our work culture also suffer. Truly professional isn't possible in Indian conservative middle class society anyway with large family and traditional customs. So work culture hampers as well.
So when bollywood is copying Hollywood, they are missing out that both the individual in stories don't have conservative big families to tell how they should live their lives. They are basically free and have money from their business and job, so they use that money to beautify themselves. Because they're not otherwise occupied like Indian family with relatives and parents and stuff.
So they look gorgeous.
Because they have money and they're not otherwise occupied to spend that money other than themselves and they work on it everyday.
Now how that is relevant in Indian society where a guy or girl suppose after passing JEE, working in some MNC.
He or she probably came from poor or middle class family where she or he probably have a lot of responsibility of their parents and other relatives in certain cases. Because it is traditional conservative society, parents are putting pressure to get married. Because it is Conservative society, sexual independence is zero hence from growing up days people would less likely to give importance to their looks to attract opposite gender. It's not in the Indian eco system.
In such a situation when bollywood copies Hollywood script to make an Indian version movie, a lot of things would look out of place.
Got it now why cliches are existing?