MONTREAL — THE appeal of city living has never been stronger. By the year 2000, for the first time, the majority of the world's citizens will live in cities rather than rural areas.Yet for millions of residents, the widely-touted opportunities of city living remain elusive. Jobs paying a decent wage are tough if not impossible to find. City dwellers in many developing nations often lack food, clean water, and sanitary facilities. "I think it's possible to imagine some very nice cities in the next 20 years, but present cities aren't headed in that direction," says Ashok Koshla, founder of the India-based Development Alternatives and a former adviser to the United Nations' Bruntland Commission on Environment and Development. Mr. Koshla spoke to more than 20 big-city mayors attending the Third Summit of the World's Major Cities here in Montreal last week. The Monitor, in a series of articles beginning today and ending Dec. 18, looks at the search for better living conditions in the world's five largest cities - Tokyo, Mexico City, New York, Sao Paulo, and Seoul - as each approaches the 21st century. (Mexico City grapples with pollution, population, Page 10.) Unlike the 1950s, when most large cities were in the United States and Europe, the majority of mega-cities now will be in Latin America, Asia, and Africa. Their growth is fueled both by escalating urban birth rates and rural migration. Even cities in industrialized nations wrestle with myriad problems that threaten to dehumanize urban living such as homelessness, drugs, crime, high unemployment, gridlock traffic, and crumbling infrastructure. In a curious fit of timing, New York City Mayor David Dinkins had just told his mayoral colleagues in Montreal about how many dollars his city was saving by its many water conservation efforts when, a few hours later, the rupture of an 87-year-old water main near Grand Central Station upset subway and bus traffic back home and prompted his early departure from the meeting. For many cities in the developing world, it is the speed of population growth that particularly undermines their ability to provide even the most basic services. Nairobi, designed for 200,000 and now 2 million strong, has doubled its population just in the last decade and expects to hit 5 million by 2000. Several mayors bemoaned the fact that the more they do for the poor, the more the poor flock to the cities. "In a poor country like India, they don't come looking for the comforts of city living - they come for jobs," says Rajinder Kuman Takkar, chief secretary of the federal administrative territory of Delhi. "So the real answer is to provide jobs for them where they live, where they were born. You can't separate urban and national development." Such cities as Beijing, Cairo, and New Delhi are trying to create rings of satellite cities that include jobs and planned housing in order to slow the move to the city core. Mayor Fred Gomu of Nairobi says rural housing committees have been established in his country to make it easier for people to build homes away from the city. "You can't expect the city to improve unless the lives of everybody improve - especially those who would otherwise end up in city slums," agrees Dr. Koshla. "The seeds of destruction are built into improving a city unless you spend at least as much money in the surrounding area." Peter Jacobs, a professor of landscape architecture at the University of Montreal and author of a key background paper on development for the mayors' summit, says in an interview that cities need new decentralized institutions that include community, business, and industry representatives. Such partnerships already exist in many places, he says, and are often far ahead of existing political structures. "There's no way ... that a centralized plan, conceived and delivered by a city government, can solve all these problems," says Mr. Jacobs. "We don't have enough money in the world." Another need, if cities are to succeed, is a broader sharing of ideas that work, mayors say. They insist that the developed world has no monopoly. Take Curitiba, Brazil, whose Mayor Jaime Lerner insists, "A city that does not recycle will not survive." He told the summit mayors that his city has the cooperation of 90 percent of all households in its recycling effort and of another 20,000 slum dwellers by offering them transport tokens in exchange for collected trash. Similarly Buenos Aires Vice Mayor Mario Krieger says his city has privatized all services from city transport to garbage, in a process by which 10,000 former city employees have become entrepreneurs.