On the field Sunday, it's the San Francisco 49ers vs. the Cleveland Browns. More and more, however, the significant games the 49ers play are against ghosts. Are they as good as Vince Lombardi's '62 Packers? Or the '78 Steelers? Or the team whose style they most resemble, the Cleveland Browns of the early '50s?

The records insist the 49ers, winners of four Super Bowls, are one shy of immortality's highest rung; many men who have seen football -- and football teams -- evolve rank the 49ers with the very best. For one season. For all seasons.

"No one has been more impressive," said Jim Finks, the president/general manager of the New Orleans Saints and whose pro career as a player and executive spans five decades. "They've met every test better than any club I'm aware of."

Anyone who compares football teams from different eras knows the exercise is nearly as foolish as it is fun. But that doesn't muzzle opinions.

Pro football wasn't even full-time employment for most players until the middle 1960s. So how could the original Monsters of the Midway, the early-'40s Chicago Bears, be on anyone's all-time short list? Because they lost only five games in four years.

Sometimes, emotion blindsides judgment. A particular collection of fans, nearing 50, believes nobody could possibly beat the late-'50s Baltimore Colts. Perhaps, and to buttress that contention those teams have six players and Coach Weeb Ewbank in the Pro Football Hall of Fame.

Has there been a quarterback superior to Johnny Unitas? A better pass-blocker than Jim Parker? A more elusive and well-rounded back than Lenny Moore? A more intimidating pass rusher than Gino Marchetti?

The heart says no. In reality, the Colts were 9-3 in the 1958 and 1959 regular seasons before beating the New York Giants for the NFL titles. In 1957 the Colts were 7-5, third in the Western Conference to a couple of 8-4 outfits. From 1960 through 1963, the Colts never finished above third in their conference and won only four more games than they lost.

The quarterback for the ages, until Joe Montana dashed into the pocket, was not Unitas but the Cleveland Browns' Otto Graham, who never failed to play for the ultimate championship as a pro. Ten seasons, 10 title games in two leagues. And, from 1950 through 1955, three NFL championships.

Graham's Browns were quite a lot like Montana's 49ers, lots more celebrated on offense than defense. And with good reason. Still, in three of those six title-game seasons, the Browns allowed the fewest points in the league; the other three years they were second.

For undiminished success, there never has been anyone like Lombardi's Packers. In the eight-season stretch from 1960 through 1967, they played for the championship six times and won five. One of the two years they missed the playoffs, 1963, their regular-season record was 11-2-1.

(Anyone under, say 35, might not remember that until 1970 there were no wild-card teams in the NFL playoffs. In addition to an 11-2-1 record failing to get the Packers into the postseason, the 1967 Colts missed out with an 11-1-2 regular season.)

The debate about the Packers and their signature '62 team essentially boils down to how various NFL watchers view the game.

"Talent is diluted now," said Redskins defensive coach Richie Petitbon, who played with the Bears in the early '60s and later for the Rams and Redskins. "Teams were better when you had {no more than} 12 teams."

The league expanded to 14 teams in 1960 and now has 28.

"There are more good teams now and more good players," said Finks. "There is more of a professional attitude by more teams than there was during that era. After December back then, some teams didn't do much until the draft in May. It's a 12-month operation now."

Petitbon: "It's a different game now. In the '60s, you still had to block and stuff. Now, it's like tag-touch. Everybody's passing. You can't rush the passer -- or do much with the receivers either."

"Teams that played for the title {before 1970} were more evenly matched," said Sam Huff, the Hall-of-Fame middle linebacker. "Now, wild-card teams have a chance."

But more often the cream stays on top. The unbeaten '72 Dolphins beat the team with the best record in the National Conference, the Redskins, in the Super Bowl; next year, the 12-2 Dolphins whipped the 12-2 Vikings in the Super Bowl.

In two of their four Super Bowl victories over a six-year period in the 1970s, the Steelers beat the team with the best record in the NFC; in the other two years, they won over the wild-card Cowboys and the 9-7 Rams.

Of those Steelers teams, the 1978 squad is considered the best. At 14-2, it was three games better than anyone else in the AFC during the regular season and beat the 12-4 Cowboys in the Super Bowl. Wondrous as it was on offense, with Terry Bradshaw, Franco Harris and Lynn Swann, the Joe Greene-Jack Ham-Jack Lambert defense probably was superior.

"Bradshaw told me and Sonny {Jurgensen} that he threw five interceptions in the first half once against Cincinnati," Huff said, "and the Steelers still left the field ahead."

In the computer matchup of great teams NFL Films did a while back, the '78 Steelers beat the '72 Dolphins in the finals. This was puzzling as well as frustrating to Dolphins Coach Don Shula, who could not imagine a computer being fed nothing negative picking an unbeaten team to lose.

"We also interviewed 19 people," said NFL Films Steve Sabol, "and the overwhelming majority also picked the Steelers."

For one team for one year, historian Sabol would choose among the '62 Packers, the '78 Steelers and one of the most recent 49ers. Perhaps the 15-1 team of 1984 that won its two NFC playoff games by a combined 44-10 and beat the 14-2 Dolphins in the Super Bowl by 38-16; perhaps the present one humming along unbeaten after six games.

For Sabol the 49ers evoke fond recollections about the Packers. Of all the team films Sabol has put together, only the 49ers and Packers players -- a quarter-century apart -- took the time to send thank-you notes.

"Had the 49ers played the Steeler defense," said Petitbon, "who knows? I'll take the Steelers, although the 49ers do have some Hall of Fame players."

Who on defense, besides safety Ronnie Lott?

"Nobody," Petitbon admitted. "But you've got Jerry Rice and Montana. And you probably can make a case for Roger Craig."

Like the Browns three decades ago, the 1984 49ers quietly allowed 21 fewer points than anyone else in the NFL. Their overkill ratio, points scored against points allowed, in the three-game run through NFC playoffs and the Super Bowl last season was 126-26.

Still, beyond the 49ers' excellence, even beyond their place in history is this hopeful message: Teams as good, or better, will come along. And surprisingly soon. They always have.