Summary form only given. Stabilizing the long-term electricity markets by providing new generation resources, is one of the most important challenges that are surfaced to the industry regulators. To deal with this complex problem, this paper proposes a comprehensive multiple attribute decision making (MADM) framework, in which the genetic algorithm (GA) is used to model the investment decisions of the market generation firms. The fitness function of the GA is itself a decentralized optimization problem that simulates the short-term behavior of these profit-oriented firms. A simple fuzzy inference system and an elasticity relation between price and demand represent the power market, as the link among all firms. The framework is augmented by tradeoff/risk analysis to incorporate the effects of the uncertainties. Finally, a realistic case study is presented to show the advantages of the proposed framework