If you gave a price range and pointed to which end of Arlington Heights (a pretty big town) you're at, I might be able to be more specific, but here are links to some posts about notable restaurants in and around Arlington Heights:
altThai, Bangkok Cafe and Thai D-Lite. AltThai and Bangkok Cafe are the dressiest. If your friend is serious about Thai food, though, I'd avoid northwest suburban Thai and take him into the city. More on altThai
here.
Bob Chinn's, a huge, noisy seafood house in Wheeling. Go early or late -- they don't take reservations -- and avoid anything "Bob's version." Do try the gumbo.
Kitakata, a fun but very casual -- maybe too casual for your purposes -- Japanese noodle house.
Lao Sze Chuan, Palatine outpost of a very special Chinatown eatery, arguably the best Chinese in the NW 'burbs, but definitely no-frills.
Pappadeaux, a big, noisy, New Orleans-influenced seafood house, with many good fish options and a Thursday lobster special. There is, however,
mixed opinion.
Sabor, a surprisingly elegant and delicious spot for nuevo Latino in Schaumburg.
Takkatsu, a unique Japanese tonkatsu specialist with a stylish interior, and great food, but a limited menu.
Yanni's, elegant Greek.
Yummy Gourmet, Hong Kong-style Cantonese in a pleasant room.
A few other options:
Francesca's Tavola, 208 S. Arlington Heights Road, Arlington Heights, (847) 394-3950. Northwest-suburban branch of the popular chain of Northern Italian-style eateries. This one is quieter than most, with a nice atmosphere. The carpaccio is a winner and pastas are consistently good.
Joe & Giuseppe, 925 Arthur, Arlington Heights, (847) 259-6448. A homey, old-fashioned, Sicilian hole-in-the-wall tucked away in an industrial strip. Try the escarole soup. (I could have sworn somebody posted about this, but I can't find it.)
Le Titi de Paris, an upscale French restaurant, has received little recent discussion here, but it used to be very good indeed.
Wildfish, 60 S. Arlington Heights Road, Arlington Heights, (847) 870-8260. A very trendy sushi and saketini spot with good-quality fish, from the same owners as Starfish on Randolph Street in West Loop Gate.