AL is very ductile, so the frames need to be more substantial than the equivalent steel, which means that compared to a good quality steel frame of similar size they can often be heavier.
AL also has a low ductile limit, which emans that at best after some years a heavily used frame can feel 'dead' and unresponsive as that limit is approached and the frame loses it's springiness. At worst it can mean failure through what is commonly terms as metal fatigue.
Steel on the other hand is less ductile, ie, it doesn't bend as much, but has a much higher ductile limit. In simple terms this emans that a steel frame will feel springy and fresh idnefinitely, provided it doesnt endure forces beyond it's ductile limit that causes it to permanently bend.
Of the two, I'd have a well crafted frame from a good quality steel over AL any day.
Titanium - wicked. Lots of pluses, not many downsides beyond the cost of the raw material and the difficulty in working it. This makes it relatively pricy, but if you can afford it.
Carbon - it's a bit simplistic to say it's "good", because this all hinges on the material and cosntruction methods used. It is possibgle to construct and extremely light, stiff and durable frame, and with care in the design it is quite easy to tune the stiffness of various frame parts to tailor the quality of the ride. As a general rule you get what you pay for - general durability, resistance to UV degradation and weakening, and the quality of any bonding etc are likely to improve with the money spent. I personally wouldn't want a carbon frime for under £500 for the frame alone, but things are improving as more firms get into this. It is actually quite a simply, if labour intensive, process to manufacture carbon frames, largely on a par with handling fibreglass, so there is no techncial reason why it will remain expensive over time.
Downside of carbon is it's resistance to impact and damage. Again though, experienced manufacturers are getting a grip on this and weaking in alloy plates etc under the sujrface layer to add protection.
So for me I'd choose a juicy steel frame, but if I had the cash I'd be quite chuffed to go Ti or Carbon fibre, if they are are of good quality.