Well doesn't it depend on the guy? I try to get some ideas from him first, because my goal is to please him, not me.
But assuming these are all within his menu, I grill steak that I marinate with my own original creation. I also love to present a boiled lobster or crab, nothing special, I think the dish stands on its own. Though my partner has done some Lobster Thermidor here, each guest receiving an entire whole lobster, that was spectacular.
And my Duck a l'Orange, actually done over charcoal briquets in a Weber domed grill, the duck's inside slathered with Grand Marnier liquor, and further steamed in "beer can" style with more Grand Marnier, is legendary.
But since I'm not a great cook, and certainly don't get much pleasure from it, if I want to impress a guy I take him to a superb restaurant, of a kind he says he'd like. As I've written here before, not only do I make a reservation, but I choose the very table, that I know is special, ask for a server that I like, and alert the owner I'll be there, so we receive personal attention.
Then I pre-pay (prix fixe), or arrange to be billed afterwards when I've left. I dislike the awkwardness of the bill presented at the table when on a date, so unromantic. And the effect on your guy, when you walk away from the table and tell him it was already all pre-paid, cannot be matched.
If he's familiar with that practice he will admire you. If he's not he will be stunned. Either way you make a favorable impression. And so for that reason I usually have preferred to take my new dates out somewhere to eat, and not risked our future on my own shaky home cooking skills.