Is love really so easily quantifiable?
I can see one thing immediately that Allison did, which Selena never will.
She loved you anyway.
For Selena, it's easy (well, as easy as loving anyone ever is, anyway). For Allison, it was a choice she made every day, even the good days. You don't seem like the type to marry someone who's dumb, so I assume she noticed that less-than-perfect meeting of the minds just as much as you did.
And the same is true for you. You worked for Allison. You don't have to with Selena.
Maybe you feel more sense of awe or wonder with Selena. But clearly, you had something else with Allison.
If you were to ask me the two greatest loves of my life, including all varieties of love, I'd give you two answers.
One of them is easy. There's that awe. That oneness.
The other was always hard. We worked. We had to. And at the end of it, we were a well-oiled machine, and losing him felt like getting my armed ripped off and then being beaten senseless with said severed limb. Just like I'm sure it would in the statistically likely event that my partner goes first.
Who did I love more?
I could never answer that.
You can measure love by the melding of the minds, as you seem to with Allison, yes.
But you can also measure it by blood, sweat, and tears.
You can measure love by the serendipity of how well you fall into place with each other without even trying.
And you can also measure it by the will you show in how hard you work to make things click.
At the end of the day, what's a more selfless choice? What is more a sign of putting your money where your mouth is?
Loving when it's easy, or loving when it's hard?
I know you and Selena have been through ****. But loving her has always been easy.
I think you underestimate yourself.
I also think it does you no good to worry yourself with what is normal. I've met thousands of people, and I've yet to meet a single one who is normal. I doubt you have either.
You're you, living your messy human life, doing the best you can. You're doing pretty good at it. You did well by Allison. You do well by Selena. Be happy with that.