My guesses are Lincoln cents, Roosevelt dimes, mercury dimes, Jefferson nickels, then Morgans, Peace dollars
I believe the lincoln cent has the distinction of the most collected coin in the world. Other data is valuable, but like someone else said remember all of those lincoln books in millions of homes. I would say for the general public: 1. Lincoln cents 2. State quarters 3. Jefferson nickels For those who consider themselves "coin collectors" 1. Lincoln cents 2. Morgan dollars 3. Not sure, maybe mercury dimes or WL halves. If anyone cares, for ancients I would say: 1. Roman Imperial 2. Greek, (mainly traditional) 3. Byzantine 4. Roman Provincial, (though if you include Jewish coins maybe #3). I leave out items like ancient Chinese since these are usually collected with all Chinese, and usually aren't collected with other ancients.
Lincolns are definately the gateway drug. They did me in. Then I moved onto other "soft drugs" like the Jefferson Nickels, Roosies, Washingtons 65-98, and Indian Heads. After that wasn't enough I started with the harder drugs: Silver, proof coins, full BU sets, etc. I am afraid of what is next. As far as "most widely collected" the Lincolns have to be the top choice. My guess among common collectors: 1. Lincoln Cents 2. State Quarters 3. Jefferson Nickels 4. Roosevelt Dimes 5. Indian Head Cents I guess if you go to a coin show just see how many binders of the above coins there are compared to all the rest. Most available, easiest for beginners to start with, least expensive to get into. I still love my lincoln collection. I think it will always be my favorite. Kind of like your first car. It might not be the rarest, or most valuable, or highly sought after, but you always have a soft spot in your heart for it.
I like this separation and breakdown -- makes more sense that way. Interesting how lincoln cents crosses over classes. That's probably why it's so high on the list. Even I have a couple of Lincoln Cents albums (almost complete minus the keys) and it's basically how I started back in 1967. Funny, I think my interest in Lincolns fell off a bit as my eyesight got worse (the problem with small dark coins!)
My lincoln cent collection went on hiatus in about 1992. Then I started it back up again in 2009 attempting to collect BU's from the 30's. Man, the money I could have saved if I would have done it sooner!