I got sick of not being able to remember all of these equivalents, so I made this little chart. You can find a more comprehensive chart by clicking here, but you have to weed through more info to get what you want.
Atari Sears Equivalent -------------------------------------------------------------------------- 3-D Tic-Tac-Toe CX2618 U 3-D Tic-Tac-Toe 75123 ER A Game of Concentration CX2642 R Memory Match 99814 U Adventure CX2613 C Adventure 75154 U Air-Sea Battle CX2602 U Target Fun 99802 75102 C Asteroids CX2649 C Asteroids 75163 U Backgammon CX2617 U Backgammon 99848 75183 ER Basic Math CX2661 U Math 99808 C Basketball CX2624 C Basketball 99826 75113 U Berzerk CX2650 C Berzerk 75168 R Blackjack CX2651 R Blackjack 99805 75602 R Bowling CX2628 C Bowling 99842 75117 R Brain Games CX2664 U Brain Games 99818 R Breakout CX2622 C Breakaway IV 99813 75107 C Canyon Bomber CX2607 U Canyon Bomber 99828 75115 R Casino CX2652 U Poker Plus 99816 75151 C (Pel[e']'s) Chmp Soccer CX2616 C Soccer 75155 U Circus Atari CX2630 C Circus 75122 C Code Breaker CX2643 U Code Breaker 99815 R Combat CX2601 C Tank Plus 99801 75124 U Defender CX2609 C Defender 75186 C Demons to Diamonds CX2615 U Demons to Diamonds 75140 ER Dodge 'Em CX2637 U Dodger Cars 75158 ER Flag Capture CX2644 U Capture 99824 75122 R Football CX2625 C Football 99827 75114 C Fun With Numbers CX2661 U Math 99808 C Golf CX2634 C Golf 75121 C Hangman CX2662 U Spelling 99811 R Haunted House CX2654 C Haunted House 75141 R Homerun CX2623 C Baseball 99819 75125 C Human Cannonball CX2627 U Cannon Man 99841 ER Hunt & Score CX2642 U Memory Match 99814 U Indy 500 CX2611 U Auto Racing 99821 75149 Indy 500 CX2611 U Race 99821 75149 C Math Gran Prix CX2658 C Math Gran Prix 75128 R Maze Craze CX2635 U Maze Mania 75157 C Miniature Golf CX2626 U Arcade Golf 99829 75116 U Missile Command CX2638 C Missile Command 75166 R Night Driver CX2633 C Night Driver 75119 U Othello CX2639 R Othello 75162 R Outlaw CX2605 U Gunslinger 99822 75109 U Pac-Man CX2646 C Pac-Man 75185 C Pel[e']'s Soccer CX2616 C Soccer 75155 U Sky Diver CX2629 U Dare Diver 99843 75118 ER Slot Machine CX2653 R Slots 99823 75111 R Slot Racers CX2606 U Maze 99825 75112 C Space Invaders CX2632 C Space Invaders 75153 C Space War CX2604 U Space Combat 99812 75106 U Star Raiders CX2660 U Star Raiders 75187 U Star Ship CX2603 R Outer Space 99803 75601 U Steeplechase* CX2614 NR Steeplechase 75126 R Stellar Track* CX2619 NR Stellar Track 75159 R Street Racer CX2612 U Speedway II 99804 75103 U Submarine Commander CX2647 EP Submarine Commander 75142 ER Super Breakout CX2608 U Super Breakout 75165 C Superman CX2631 C Superman 99845 75152 ER Surround CX2641 C Chase 99807 75105 C Video Checkers CX2636 R Checkers 75156 ER Video Chess CX2645 U Video Chess 99817 75181 R Video Olympics CX2621 C Pong Sports 99806 75104 C Video Pinball CX2648 U Arcade Pinball 75161 R Warlords CX2610 U Warlords 75127 U Yars' Revenge CX2655 C Yars' Revenge 75167 U C - Common U - Uncommon R - Rare ER - Extremely Rare UR - Unbelieveably Rare EP - Prototype (Never released, may or may not exist)