I would say based on history the 2.2L is the most reliable. (I feel a heated discussion coming from this one) MANY people discourage others from getting anything with the 2.4L. Because it's history is not forgiving whatsoever. It has a long history of blowing head gaskets and cracking heads. Although a majority of this was early on, and by the time it made it to the year 2000, it was a very fine little engine, but too little too late in many eyes, and the ditched it for progress and developed the "Ecotec". So, many will say no to the 2.4L, but I personally don't believe it would have significant problems. I own a '95
2.3L, (almost identical engine) and haven't had any of the problems associated with it's bad history. The 3.4L I guess is so-so. Some have nightmare problems with them, others don't. But one thing stands true from what I've heard, they are a pain to work on, and expensive. So though the 3.4L offers by far the best performance, and may very well be as reliable, should you have problems, it could get ugly quick. So for what you're asking I'd say: #1 2.2L #2 2.4L #3 3.4L
Tony