In football, basketball and hockey, as in baseball, any set from the 1940's, 1950's, 1960's, and 1970's in near mint or better condition is considered very rare and valuable, and sets in the 1980's are beginning to take that shape as well since unopened material is being sold and opened constantly.
Here is a quick list of cards you should check for in the 1980's.
Baseball - 1980 Rickey Henderson rookie card (Topps), 1982 Cal Ripken, 1983 Tony Gwynn, Ryne Sandberg, Wade Boggs, Julio Franco
1984 Don Mattingly, Joe Carter (Donruss) 1985 Roger Clemens, Kirby Puckett, Mark Mcgwire (Topps) 1986 Jose Canseco (Donruss, Fleer) Fred McGriff (Donruss) 1987 Greg Maddux (Donruss), Barry Bonds, Rafael Palmeiro, Barry Larkin 1988 Mark Grace, Tom Glavine, Roberto Alomar 1989 Ken Griffey Jr., Randy Johnson, John Smoltz, Gary Sheffield, Craig Biggio
Basketball - Any 1980's rookies (basketball from Star Company 1983-86 and Fleer 1986-89 is rare and highly sought after). Here are the most rare years of cards, so an entire set would be ideal in these years.
From the 1980's, these are the best rookie cards to have.
1980-81 Magic Johnson and Larry Bird (even more valuable in near mint to mint condition)
1983-86 Star Michael Jordan, John Stockton, Hakeem Olajuwon, Clyde Drexler, Isiah Thomas, Patrick Ewing, Charles Barkley, James Worthy among several others (if you have any Star Company cards from these year they are quite valuable) An entire set of sealed team bags from any year including all of the teams can be worth upwards of $1,000 or more in highly graded condition.
1986-89 Fleer Same as above and Reggie Miller, Scottie Pippen, Dennis Rodman, Horace Grant, Detlef Schrempf, Ron Harper, A.C. Green
1989 Hoops David Robinson
Football - 1981 Joe Montana, 1982 Lawrence Taylor, Ronnie Lott 1983 Marcus Allen, Jim McMahon, Mike Singletary 1984 (big year) Dan Marino, John Elway, Howie Long, Darrell Green, Jackie Slater, Eric Dickerson 1985 Warren Moon, Richard Dent, Irving Fryar
1986 (big year) Jerry Rice, Steve Young, Bruce Smith, Boomer Esiason, Reggie White 1987 Doug Flutie, Randall Cunningham, Jim Kelly
1988 Vinny Testaverde, Bo Jackson 1989 (Score is rare this year and highly valued) Barry Sanders, Troy Aikman, Cris Carter, Sterling Sharpe, Michael Irvin, Thurman Thomas