Please Note

Ok first I would like to keep the comments civil as this is not meant to stir up arguments about which game is better and takes more skill. (Though I know it is hard to resist)

Second I'm sure there are many people who don't know the differences between LoL, HON, and DOTA, so I went out and found a pretty decent writeup of the major differences between LoL and DOTA. I will admit that I don't really play HON so if people know the MAJOR differences between HON and DOTA please leave those in the comments.

Thirdly some of these maybe outdated as LOL, HON, and DOTA frequently patch.

I hope this is informative to people.

Major Differences between LOL and DOTA

• Champion selection is limited to the "free to play" champions (which are rotated on a weekly basis) or the ones you have purchased using in game points (Influence points) or real life money (converted into Riot points).
• Maximum level is 18. With the exception of (as of writing this) 2 champions, Udyr and Karma, this gives your Q, W, and E skills 5 levels, and your R ultimate 3 levels. For Udyr, as he has no true ult, but rather 4 basic skills, you could have a 5 5 5 3 setup, or a 5 5 4 4 setup, or any combination therein. For Karma, her ult is given at level 1 and never levels up, giving her Q, W and E skills 6 levels each.
• No denying. This includes towers as well as creeps/minions. You can still deny by keeping enemy champions out of the kill radius / prevent them from last hitting, but there is no "auto-attack your own minions" to deny.
• No gold loss on death.
• Towers hit a lot harder and do more damage to you the longer they've been hitting you, making early tower dives a lot riskier and making towers much safer to defend against.
• You can only kill the enemy base/nexus by killing an entire lanes towers then its inhibitor then subsequently the 2 nexus towers before destroying the nexus other lanes towers do not need to be destoyed.
• The ranged/melee barracks have been merged into a single building called an inhibitor, and instead of bolstering the melee/ranged minions in that lane when destroyed, it instead makes a single, powerful melee unit spawn with every wave. Inhibitors respawn over time.
• There are far fewer "active" items (click to use) and the focus is more on increasing your passive stats.
• Every champion has a passive ability that is somewhat integral to their playstyle or their character flavor. These passives are always active and require no skill points. For example, the champion Zilean increases all allies' experience gain by 8% always. A more active example would be the character LeBlanc, who spawns a mirror image whenever she drops below 40% HP (occuring at most once per minute).
• There is a 3v3 as well as a 5v5 map, meaning there are two separate meta-games to identify (though most people play 5v5).
• Some of the larger neutral creeps provide passive buffs that provide a visual effect as well as a bonus to attributes. For example, the Golem buff provides mana/energy regeneration and cool down reduction.
• There is a large neutral creep called the dragon that provides teamwide gold and experience. This is often contested through the mid-late game and is a prime target for jungler champions to kill.
• The "boss" neutral creep (Baron Nashtor) does not provide an item (like Token of Life), but rather teamwide gold/exp and a passive buff that greatly increases health/mana/energy regen as well as additional attack damage and ability power.
• You get to choose 2 additional "Summoner Abilities" that are universal regardless of what champion you pick. Some examples of these are Ghost (temporary speed boost and unitwalking), Flash (short range teleport), Ignite (scaling damage with a DoT and reduced healing/regen component), and Clairvoyance (short cooldown, small radius map reveal). There are others too, of course.
• No river runes.
• You may passively increase your champions' stats by purchasing "Runes" outside of the actual in-game interface. These runes are purchased using points you earn by playing games (winning or losing).
• Additionally, you may increase your champions stats / enhance your "Summoner Abilities" / provide passive effects through the mastery system. The mastery system is a simplified version of a talent tree (akin to Diablo 2, World of Warcraft, etc.) with points being earned as you level your summoner (your account), which is done by simply playing games.
• Ability to return to base (free, no need to buy it, no item slot taken, no cooldown)
• Improved juking - instead of sneaky paths between trees there is "brush" (bushes/grass) system - brush blocks line of sight of those outside it and provides bonuses to some champions/heroes
• Map is symmetrical with the exception of the placement of the Dragon and Baron "boss" creeps.
• Shields system - damage shields are dynamically displayed as a gray extension of the healthbars. Purple extensions indicate magic-only shields.
• It's possible to bind smartcasts (cast instantly on keypress on the area the cursor is hovering over, not on an additional mouse click)
• No secret shops or outposts. All items are purchased at the base shop.
• The Shop's combination items are displayed in a tree, making it easy to see which items combine into what.
• There exists no buy-backs. What this means is that once your champion is dead you must wait out the full length of the death timer (which increases based on champion level), whereas in DOTA one could spend money to immediately bring their champion back to life, thus skipping the death timer.

REFERENCE:http://gaming.stackexchange.com/questions/10173/what-are-the-differences-between-defense-of-the-ancients-dota-and-league-of-leg