I'm with you pureshipper.  Finn and Bubblegum were very forced.  I don't think Bubblegum ever saw and still doesn't see him as her equal, and for someone her age, I believe that's important.  Even when she deaged herself, I don't think she viewed him as anything more than a play companion.
Now Marceline is someone who has lived as long as her and constantly challenges her.  Bubblegum needs someone who will call her on her B.S. and I think deep down she knows this.  All her candies are 'yes ma'am' types.  Even Finn doesn't ever question her.
Bubbline forever!