Another Novel idea.

I'm sure that we all have a novel or two on the go or hidden away in a drawer.
My first novel was finished about 4 years ago or maybe 3 I'm not sure. I sent it our to an agent or two but with no joy. Then an author of dozens of novels under 3 different names who clearly has more knowledge of this sort of thing pointed out that there would be a problem with the book that I won't bore you with. She was by the way completely right, I just hadn't seen it before. I thanked her for her advice and we agreed that I should concentrate on another book which I had just started and we thought would have better prospects. That book was finished a couple of years ago. That too has been sent out but still with no joy. Everyone I have sent it to has been very positive about the writing but say that they're just unsure of where they would place it. I still really like that book and hope to see it in print one day. Then I started my third book which was I thought an even better idea than the second one. But when the dark stuff was happening last year it got neglected and as yet I've still not found my way back into it. This week I started my fourth book and I think this is the strongest idea yet.
I'm only a few thousand words into the first draft but I do believe that this will be my best so far.
So as each one gets a bit better than the one before, presumably as I get more experience and learn the craft, how many do you reckon I will need to write before one is good enough to be accepted?
Just out of interest I'd love to know how many books you have written or on the go.