Congressional leaders praised President Reagan yesterday for opening up a dialogue with Soviet leader Mikhail Gorbachev at the Geneva summit, but some expressed disappointment that the two leaders failed to produce real progress on arms control and other points of conflict between the superpowers.

The generally positive but subdued response to the summit outcome was reinforced by Reagan's address last night to a joint session of Congress, which lawmakers said highlighted both the importance of the Geneva talks and their limited achievements.

Senate Majority Leader Robert J. Dole (R-Kan.) said the most important achievement was simply "the fact that they met.

"They didn't have to do anything," Dole added. "The president's tone, in my view, was perfect."

Calling Reagan's address to Congress "a good speech," Sen. Patrick J. Leahy (D-Vt.) said, "The thing I liked most is that they will be meeting yearly . . . . If anything will cut down suspicions, it's yearly meetings."

House Minority Leader Robert H. Michel (R-Ill.), reflecting the cautious congressional reaction, said, "I don't think we can weigh successes and failures when we are geared up for such a long haul. The positive thing is the establishment of the beginning of a process."

Even before Reagan's helicopter landed outside the Capitol shortly after 9 p.m., congressional leaders said the summit would reduce world tensions. But they stressed that the Geneva talks were only the first of many steps toward improved U.S.-Soviet relations.

"We believe the discussions in Geneva have begun the important process of reducing tensions between the United States and the Soviet Union," House Speaker Thomas P. (Tip) O'Neill Jr. (D-Mass.) said in a statement issued by the House Democratic leadership. "We are encouraged by the joint statement's affirmation of the principle of significant nuclear-arms reductions. We applaud the joint pledge to seek agreements on the elimination of chemical weapons."

But the statement added, "We had hoped for more substantive progress in arms control, human rights and regional conflicts . . . . We assume and hope that at the very least both superpowers will continue to adhere to the SALT II and the ABM [Antiballistic Missile] treaties."

The praise for Reagan was bipartisan, but while Republicans lauded the president for what Dole called "a job well done," the Democrats emphasized what they said were the limited achievements of the Geneva talks.

Senate Foreign Relations Committee Chairman Richard G. Lugar (R-Ind.) said that Reagan, in his two days of face-to-face meetings with Gorbachev, "significantly advanced the cause of world peace."

"The chemistry is different now, and that is very significant," Lugar added.

Rep. William S. Broomfield (R-Mich.), the ranking Republican on the House Foreign Affairs Committee, praised Reagan "for having accomplished his main goal" of improving the tone of U.S.-Soviet relations "without compromising our security."

But even Republicans described the outcome in modest terms and noted that the major disputes between the superpowers remain far from resolution.

Sen. Dan Quayle (R-Ind.) said the summit was "an important step toward reducing tensions between the superpowers," but added, "At the same time, it is apparent that critical issues on the agenda, including the Soviets' noncompliance with past treaties, regional conflicts and the Soviets' abysmal record on human rights, remain unresolved."

Sen. Nancy Landon Kassebaum (R-Kan.), calling the tangible results of the meetings "modest," said, "I believe the summit has opened the way for serious and detailed negotiations on a series of critical issues . . . . "

Democrats were more blunt in their assessment of the summit's outcome. Two of the leading Democratic contenders for the 1988 presidential nomination, Sens. Edward M. Kennedy (D-Mass.) and Gary Hart (D-Colo.), issued similar assessments of the Geneva summit, emphasizing that little was changed by the talks.

Kennedy called the Geneva meetings "a step forward," but noted that "for the present, the various agreements signed do not change the fact that the nuclear-arms race goes on, existing arms-control treaties were not reaffirmed, the war in Afghanistan continues and the plight of Jews in the Soviet Union is unchanged."

Hart praised the "positive mood" created by the summit, but added, "The reduction of nuclear weapons should have been the foremost goal of the summit, yet it has been largely overshadowed if not ignored. However grateful we all are for the apparent change in mood that results from this meeting, we cannot deceive ourselves into mistaking symbolism for concrete action . . . . Now the administration must tell the American people where we go from here."

Sen. George Mitchell (D-Maine) said Reagan gave a "good speech that reflects the summit itself: there was little substance but much hope for improved relations in the future."

"On style, the summit was a success, on arms control it was a flop," said Rep. Edward J. Markey (D-Mass.), a nuclear-freeze proponent. Markey said Reagan deserved "polite applause, but not a standing ovation."

Sen. Sam Nunn (D-Ga.), ranking Democrat on the Senate Armed Services Committee, noted the mild tone of the president's remarks last night about the Soviet Union and said he thought this reflected "the overall gain in terms of the atmosphere" from the summit.

House Foreign Affairs Committee Chairman Dante B. Fascell (D-Fla.) said the summit ended "on the plus side" but added that he was disturbed by the absence of a specific reaffirmation of the SALT II and ABM treaties. This was "a noticeable gap," Fascell said.

The sharpest criticism of the outcome came from an anti-nuclear group outside of Congress, the Union of Concerned Scientists, which ran television ads before the summit urging Reagan to bring back an agreement. "Basically, we are very disappointed," said Howard Ris, the group's executive director. "We see not a single shred of progress on arms control. It appears that President Reagan's rigidity on 'Star Wars' [the Strategic Defense Initiative] may have lost a unique opportunity to extract concessions from the Soviets on offensive weapons."

David Cortright, executive director of SANE, another antinuclear group, said Reagan would gain credit for "some progress" in overall U.S.-Soviet relations at the summit. But he said his organization felt "deep disappointment" at the failure to achieve any progress on arms control.

Among those who praised the outcome of the summit yesterday was Defense Secretary Caspar W. Weinberger, who remained behind in Washington during the talks and whose presummit advice to Reagan to take a tough stand on arms-control issues -- contained in a letter that was leaked to the press -- caused a furor.

"I am very happy with the outcome of the Geneva meeting," Weinberger said. "It was indeed, as the president hoped, a fresh beginning, and portends very well for the future."

Conservative spokesmen expressed relief that the summit did not produce a new arms accord.

"The good news, it could have been worse," said Howard Phillips, chairman of the Conservative Caucus. "My concerns are with what hasn't been said -- whether the president will be able, having had these meetings with Gorbachev, to extricate himself from what seems to be unilateral American adherence to the SALT II treaty."