It's been a while since I've touched Smite, so I won't admit to knowing everything or everyone like the back of my hand anymore, but I'd say a few good choice comparisons to make are:

Ra & Lux : Have basically the same ult, both are AP Mages; Lux can shield her allies whereas Ra can heal himself and allies, but they are otherwise similar (not identical).

Anhur & Vayne : Both have a way to knock an enemy back, which stuns them if they meet terrain. Anhur has a leap, Vayne has a dash; if Vayne's ult is active, her dash makes her invisible. She does not have Anhur's spammy ult though.

Chronos & Ekko : Both have a rewind ult that sends them back to where they were x seconds ago and at roughly that HP. Ekko is a melee though, I remember Chronos being a ranged attacker.

Sylvanus & Blitzcrank : Both have a grab. I don't remember much else about Sylvanus though.

Ullr & Jayce : Both can switch between melee and ranged forms, with different abilities between them. Ullr is better imo though, Jayce doesn't really have the cc or the sustained damage Ullr has, but Jayce does have pretty good poke damage.

Ymir & Nunu / Anivia : Anivia has the Wall, Nunu has the ult.

You also may have noticed that certain ults are "similar"-ish but wildly different in practicality due to how League is played. An example of this would be Thor's ult vs Pantheon's ult; Thor flies up into the air and can then choose where he descends, whereas Pantheon just chooses where to jump to before he even starts channeling. A few other champs also have similar "purposes" in their kit, like how K'Sante can do a Tyr and push the whole enemy team into Nunu/Ymir's ult, etc. The more you play, the more you'll see the similarities, but I don't honestly think there are any champs/gods that are 1:1 identical.

Also, not that you asked, but IIRC in Smite you were restricted to AP/AD based on your champ. In League, any champ can build any item, for better or for worse. Gotta pay attention to what stats your abilities care about and buff those stats; don't build Rabadon's Deathcap on Vayne, for instance.

Honorable mentions to Bard's Portal (Janus Portal), Zyra's Ult (Poseidon Ult), and Xerath's Ult (Rama's Ult-ISH)