Chavez upset big American money. In his first few years in power he changed foreign oil companies' cut from 84% of the barrel price to 70%, and he also reduced the amount of oil they were allowed to produce. ExxonMobil et all saw a dip in their profits overnight (at a time of unprecedented growth). He used the money the new deal raised to build houses for the poor (replacing shanties), and to provide free health care and education. In turn, this ensured he was a fairly popular figure among the poor (though not universally liked) and utterly despised by the rich immigrant elite who used to run the country. Then he set about reclaiming millions of acres of unused land, requiring landowners to sell it to the poor on the cheap. In response to an attempt to buy it's unused land, Heinz closed it's Venezuelan plantation and sacked all the workers. Chavez then sent the military to repossess the plantation and restore the workers to their jobs.
He upset the oil companies again when it came to heavy oil, proposing a guaranteed (but fixed) $50/barrel price on a 30-year contract. Venezuela would become rich, the oil companies would have a more stable income far from the worries of the Middle East and a vast supply of cheap Venezuelan oil would keep oil prices down. The deal was rejected. If Venezuelan heavy oil stays in the ground, and the US and Britain keep the middle east in turmoil, the price of oil (and oil company profits) will continue to rise.
It's the usual short termism. Venezuela is now China's largest foreign infrastructure investment - they've invested heavily in the country since around 2009, attempting to fix many of Chavez's failed infrastructure projects. As it stands, if Nicolás Maduro wins the upcoming election, it seems probable that the Venezuela's heavy oil will find it's way out of the ground via Chinese companies - it's China that's helping to build the infrastructure needed to make it happen. Time will tell if it will happen under the terms that Chavez wanted - if it does, then expect a steep drop in oil prices in a few years' time.
On the man himself; like every successful politician, he did good things and bad. There isn't a single one of them without blood on their hands. Measured against his peers, he was an idealist and an administrative failure. I do, however, admire his courage and resilience, his dedication to his ideals and principles. It didn't go to plan, but he gave socialism his best shot, and changed the lives of millions in the process (For better or worse? Either way, at least he tried to liberate Venezuela's poor).