St. Luke's Guild,
Well, I wouldn't actually dream of trying to claim superiority for either Chaucer or Spenser. I think they're different enough that there isn't really a way of saying who's "better," though naturally as a Renaissance scholar I'll give Spenser the edge ;).
As for naming periods, it is, as you say, slippery. In terms of literature the Renaissance period is generally said to begin on the continent with Petrarch (1304-1374), just as it does about the same time in the arts with Giotto. The cultural changes of the Renaissance moved slowly geographically however, and England's a bit behind in terms of the revival of the classics and all the rest. The English Renaissance is later in terms of nearly every aspect of the culture and doesn't really begin until about the 16th century. Basically the culture of England in the 16th and early 17th centuries is more like Italy in the 14th and 15th centuries, with the visual arts lagging behind a bit more than the literature, due in part to the reformed church--it's not until Inigo Jones (1573-1649) in the Jacobean era, for example, that England starts seeing anything like the kind of architecture that Italy saw around the quattrocento with the likes of Brunelleschi and Bramante.
In terms of literature, More's Utopia (1516) marks the early English Renaissance, and soon after Wyatt (1504-1542) and Surrey (1517-1547) introduced the sonnet, and along with it the vogue for imitating Petrarch, into English. The 1590's is an important decade among English literary scholars, and considered a highpoint of the poetry, when everything started really taking off. In terms of literature, the English Renaissance is then usually marked as ending with Milton (1608-1674), with Spenser (1552-1599) and Shakespeare (1554-1616) falling squarely into what is sometimes termed the high English Renaissance (though some distinctions are made in the types of shifts that occur between the Elizabethan and Jacobean eras within this larger "Renaissance" period). Since you asked, Cervantes is usually considered a Renaissance author as well, though I'll agree that he does straddle more of a divide into a later period. Since all of this does get rather confusing, scholars have taken to referring to a very broad period as "Early Modern," which seems to cover everything from Petrarch and Giotto to Milton and Rubens very neatly. It's not a term that's caught on much outside academic circles yet though.
Laying aside the picky details as to what we call these periods, I find it interesting that you associate Spenser on a stylistic level with the baroque. I had always associated Rubens' style somehow with Milton's poetry, and I think of Shakespeare in something of a Caravaggio or Rembrandt light, but Spenser I generally envision in terms of earlier Renaissance art. At times those set battles on a plain (in which the combatants are described symbolically as animals), or certain of the processions he describes have almost a flat and symbolic Medieval feel, and I think the archaic language and, to some extent, the allegorical nature of FQ in general tends to hark back to an earlier style. At other times the images come out much more fully of course. I always think of Calidore's vision of the graces in book 6 as being much like Botticelli's Primavera for example, and the characters of book one's House of Holiness I always see as being somehow being rather like the figures of a Filippo Lippi or a Benozzo Gozoli for some reason, while I've always thought Bosch would do a bang up job depicting the Masque of Cupid in book three. But enough with the speculations of my own fancy. :lol: It's interesting the way we all envision things differently as we read.

