1) I don't think that at most BBs in the U.S. analyst bonuses are yet as low as $20k, even for first years. All-in should still be over $100k and good luck making that in consulting or corporate finance.
2) Yes banks are slimming, but firstly: Goldman isn't "cutting" its 2-year program. From my understanding, they're changing the structure so that newly hired analysts just aren't automatically put on a 2-year contract, with the goal of making them stay around longer. GS is still hiring analysts, however, and analysts will still be able to leave and go to PE if they desire (someone please correct me if my understanding is not correct). And you also cite UBS, specifically London - arguably the weakest BB in one of the weakest possible markets right now. I'm not surprised they have cuts but their situation is not representative of all other BBs in the U.S. and/or other non-Europe markets right now.
3) MM investment banks and corporate finance positions would not be generally comparable to BB IBD in terms of exit ops - the job landscape has changed, but that hasn't. Same for non MBB consulting. For MBB, the exit ops are definitely strong, but people should probably decide between banking and consulting based on their interests. Do you want to help a company go public, buy another firm/sell itself, or raise debt? Or do you want to advise a company about how to optimize its revenues, reduce costs, or simply come in to support a strategic decision your client has already made? Some people might prefer to stay in NYC 7 days a week, even though they have long hours, than be constantly travelling to (typically) unexciting places across the country. I don't mean to knock consulting - others might think that what I wrote presents a slanted viewpoint, and that may be true (it's just my impression). But at the end of the day, banking and consulting are very different and people should think about what they really want to do for 2 years.
4) Entrepreneurship is awesome. Everyone that I know wants to do it eventually, but the thing is, it's hard to feel ready to pursue a start-up immediately after graduating. Banking still offers a great foundation to learn corporate finance/how businesses operate financially, especially for students that didn't study business in college. I'll concede that consulting also offers a good jumping-off point for entrepreneurship, with a greater focus on strategy than finance.
5) The last point is good to remember. There are lots of things out there, and no one "perfect job."