Honestly, it is crap at first.
My two are similar age gap. I felt awful for having totally changed DD1's world when DD2 arrived. Our beautiful one-on-one relationship was put totally on the back-burner as i cared for DD2- I breastfed so it was all on me in terms of feeding, which was fine, but it meant way less time for DD1.
I mourned that loss in a way and felt that even though I loved DD2 I didn't love her as much as DD1 and I felt awful about that too. This, by the way, was mixed in with equal parts of being elated and happy and exhausted and tearful but generally grand really, and I had great support from DH and family thank goodness.
But I still felt shite about it all! At times!
BUT- DD1's relationship with DH blossomed as a result and so she really really didn't suffer. She had great attention , but just from the other parent more so for a while.
And then as DD2 grew I realised it wasn't that I loved DD1 more, it was just that toddlers are way better (IMHO) than newborns. DD2 emerged into toddlerhood and utterly immersed me in love, an absolutely equal love to the one I had and have for DD1.
And now I have a 4 year old and a 6 year old who go from killing each other to playing together like angels, to off the ball incidents that make me feel more referee than parent, to cooking up madcap mischief to unleash on DH and me and laughing like they'll never stop, but who are, genuinely, each other's best friends.
And^^ that's why I now realise that having number 2 is a long game. At first it's a bit shit, but ultimately it's so fricking amazing that I actually have tears in my eyes now
thinking about how much I love them and how much they enrich our and each other's lives.
So in summary, own the guilt. It's just part of the process and it will be worth it!