I felt something close to this only once with a guy, but we had only been going out for about 3 months, and he disappeared after this, so I was yet to discover his flaws at that point.
What I saw in him that made me feel like a long term relationship was possible were:
1. He was financially stable, not particularly rich, but he had a secure job, worked hard and was careful with his money. I work very hard for financial stability myself, because I'd like to have a family one day, so it was important that we matched on this level.
2. He was considerate and protective. If we stayed out late, he would walk me to my car. One time, I wanted to leave something in my car in the mall parking lot, and even though it was daytime, he followed me just to be sure I was okay. If I had to work the next day, he would make sure to end our calls and meet ups early. When we went out to eat, he would make sure it was vegan friendly for me.
3. He was the opposite of me and similar in ways that were important. Our personalities were different, but we wanted the same things in life. We had similar values aka wanting a family, responsibilities towards parents and siblings, spirituality, living humbly/saving money.
4. He was calm, peaceful and positive - I felt more zen around him
5. He treated me with respect. He sort of made it clear that he was attracted to me but he didn't try to push intimacy early on.
Hope that answers the question